Glass Fuselage
Actually, I do have a fiberglass sailplane fuselage, that I aquired way back in the early eighties when I was actively flying sailplanes. It's likely pretty out of date design wise, but I'll do my best to give you a basic description. It was made in England. It has a tapered fiberglass tube for a tailboom, like the old Grand Esprit and a fiberglass forward fuselage that's round in cross section, with a fairly pointed nose, and wing roots moulded in. I have no idea what airfoil the wing roots are....something from that era. It's not small in cross section, and there's plenty of room for standard size servos etc. I can dig it out and get some dimensions and weights if you are interested. Pictures are a little more difficult, but not impossible as I don't have a digital camera.....yet!
At a guess, I'd say it's 3" to 3 1/2" diameter thru the forward fuselage. You may be looking for something a little more "up to date", and smaller in cross section. Let me know if you're interested in more info.
Cheers, Nigel