Correct, I use the same cover and frame size. I usually blow some air into the Fuelselage after I've installed it to make sure it expands as much as it can. You can do the same after you've added some fluid, see which works best for you. Getting the Fuelselage to fit well can be tricky. Some days I get it straight away, other days I can spend 15 min fiddling before I succeed.
By the way, I also use a Camelback mouthpiece instead of the one provided with the Fuelselage. The one from Camelback closes off the drinking tube, so that the fluid doesn't fall back down. This makes sipping easier as you don't have to suck the fluid up the drinking tube. The Camelback mouthpiece is actually made for a smaller diameter tube, but you can fit it on there because its flexible.
Felt IA Calpac mods on Shapeways:
800ml Specialized Fuelselage (XS/S)
1000ml Specialized Fuelselage (M/L/XL)
DIY cover
By the way, I also use a Camelback mouthpiece instead of the one provided with the Fuelselage. The one from Camelback closes off the drinking tube, so that the fluid doesn't fall back down. This makes sipping easier as you don't have to suck the fluid up the drinking tube. The Camelback mouthpiece is actually made for a smaller diameter tube, but you can fit it on there because its flexible.
Felt IA Calpac mods on Shapeways:
800ml Specialized Fuelselage (XS/S)
1000ml Specialized Fuelselage (M/L/XL)
DIY cover