Hi Dave, the servo was the biggest one that was available on GiantCod/GiantShark at the time I bought it (~2011). I think it only cost me £15 and was rated at 20kg/cm. GS is no longer in business but there will be other servos out there of equivalent size and power, no doubt somewhere on HobbyKing.

I've got a couple of pictures of the insides of Flatulence but I'm just about to head out so will post them once I'm back. If you're planning on being at the November Iron Games final I'll have it there too so you'll be welcome to have a nosey in about it.