Now both factions have Hargh'peng Torpedoes. Naturally, Peng boats have sprung up. I tried it on my Chang-B'rel (Don't get too scared, the results were less than stellar, as you'll see). So, if someone wants to have this build at optimum, the first place to start is the ship you're flying. So, I'll give you a run down.

I'll start with the KDF. Story-wise, they invented them. Game-wise, they have easier access.
B'rel Retrofit - NOT recommended. Even if you have their firing buttons keybound, or have them on Autofire, you will partially decloak when firing. The rate of fire will keep you that way, making you an easy target. If you're going to use this ship for your boat, decloak after the first shot unless you want to very quickly explode. The turn rate and Universal BOff slots are decent for it, but if you really want to use it, spec your BOffs into healing powers. No torpedo abilities affect this weapon.
Marauder Patrol Cruiser - Moderate recommendation. This ship has a decent healing ability. It's got 8 weapon slots. The only real concern is the turn rate, which is... well, it could be better.
Varanus - Not recommended. 6 weapon slots, immoderate turn rate. I'd rather recommend this class as a healer FOR the boat, especially if it's a B'rel boat.
Kar'Fi - Midway. Immoderate turn rate, 7 weapon slots... but the S'Kul fighters would do you better. It's really up to you, but it wouldn't be MY first pick.
Guramba - Recommended. Good turn rate. Good hull rating. Even if it only has 7 weapon slots... I don't recommend going into Siege Mode, because of the Turn Rate reduction, but the Javelin could be useful. It'd be a hard pick between this and the Marauder.

Now it's time for the Fed side. Granted, it takes much longer to make a Peng boat, but the prospects for a Fed boat are much better.
Galaxy-R - Moderate recommendation. The BOff slots are alright, the Turn rate could be better, but it has 8 weapon slots. Couple that with Saucer Separation, and it would make a formidable Peng boat, especially when supported by the Saucer's beams.
Galaxy-X - Not recommended. The Cloak and Spinal lance are great, but the downright HORRID turn rate is just unacceptable for a build of this type. I fly a Galaxy-X regularly, I've put in turn mod engines AND consoles, and it's still horrid. Don't do it.
Tactical Escort-R - Midway. The ship's BOff slots aren't exactly friendly to the build, but its turn rate and Cloak give it a slight edge. It only has 7 weapon slots, but that's pretty good.
Multi-Vector Advanced Escort - Midway. Like the Defiant, the BOff slots neither help nor hurt the build, and the turn rate does help. I don't recommend using Multi-Vector Assault Mode, it sets you out of the build, but it DOES give you turn rate and Beam boosts.
D'Kyr - Midway. Decent turn rate, the Sensor Analysis will boost damage, and the BOff Slots can give you a decent heal. The drawback is that Subsystem Targeting would be useless.
Nebula - Recommended. While the Subsystem Tarteting is again useless, the Sensor Analysis is still boosting damage. The boon for the Nebula is that its Tachyon Detection Grid would be able to penetrate cloaks, allowing it to be a direct counter to any B'rel Retrofit setup while allowing you to be a healer, both self and team.
LRSV-R - HIGHLY recommended. For the same reasons as the other Science Vessels, it already makes a good boat. It gets better thanks to the Ablative Generator, which only allows you to fire torpedoes. Hargh'pengs are torpedoes. For 15 seconds, you become a flying tank. A half dozen torpedo launchers and 90% damage resistance. This is probably the best Peng boat ship in the game.

With this in mind, go build yourself a Peng boat and have fun. I hear the Borg really aren't fond of the Hargh'pengs, you should test your build on THEM first.

And with one post we see why it is of utmost importance that they get a one per customer fix set up for these torps ASAP.

The B'Rel R is fine with Pengs it cannot sit int he middle of the battle it needs to be a quick deploy artillery ship and a Jam sensors is key that way if by chance someone finds you you can JS and EPtE and EM out.

The Intrepid is perfect for Penging.

Though, please note, that I do not endorse Peng spamming in any way, shape, or form. I hate Peng spammers. It's all good for the Klingons to do it now as sheer revenge (especially to watch people cry about them when before they simply told Klingons l2p or use Hazards), but even that's got to stop sooner rather than later.

This sums up my feelings on Beam boats, but no one seems to have a problem with THEM anymore...

There were/are issues with beam boats?

I remember them fondly. So many arguments... It had something to do with a FAW exploit, and people in PvP were planting all beams onto cruisers and FAWing everything. People were complaining about it, there were more than a dozen forum topics about it. I'm surprised you DON'T remember it...

I like one on each side of my ship, I don't PVP but understand the complaints. I don't think its right to make a changed based on pvp issues that will hurt pve. Limiting it to one on each side I'm cool with, most PVE ships are not torp boats.

This game also has a habit of not grandfathering gear meaning, if people have it slotted before the change. All the change will do is hurt future toons.

They are easy to deal with. People just do not want to. They are also easy to shut down. Again people just do not want to do it. This is just asking people to make them. You can not paint a target faster on you then to not have things like Jam sensors or Hazzard Emiters yet many people go out of the not to have them saying that are part of the problem.

Those are issues with FAW, not beam boats. Most of my Cruisers and Scis are beam boats; they're perfectly viable and OK to use. As long as you're not using FAW.

Even after FAW got it's "fix" a few patches ago, it's still OP. That's why none of the serious PvPers and fleets use it.

A lot of ships can't afford to have Hazards, much less Jam Sensors which is highly situational at best.

Defiant, Excelsior, Assault Cruiser, Fleet Escort, etc only have 2 Sci slots. Tractor Beam, TSS, and SciTeam are all more popular (and in some cases, more valuable) choices than Jam Sensors.