I would really like to build a GP Extra 300s .60, but to me it looks like the fuse length is just too short, and comparing the fuse length to the wingspan (while probably an arbitrary comparison) on several different extra's, it seems that the GP Extra .60 fuse should be a few inches longer.

My question is what can I expect to happen if I kit bash to make the fuselage a bit longer?

Thanks!

three things
It will be a bi-tch to do
It will get tail heavy
It will enhance what is called "yaw stability"--meaning it will be more stable against side to side motion
Having said that .
This is a great model -- light and very scale.
here is an easy fix:
shorten the span 9% and increase the chord about 1/2 inch
accomplishes the same thing basically except the overall plane will not be dimensionally as large as one where the fuselage is increased.
Shove a new 80 single in it with a can muffler (easy to fit) and watch the weight . like a hawk!
should be a great power to weight and responsive plane .
Making the plane slightly more "square" really makes for a better aerobatic setup.

Example 85"span x85" overall tip spinner to tip rudder .

Why bother? Are you worried about pitch & yaw stability? -- it's not a real problem with this aircraft.

wrong model -I was looking at the big kit not the 60 arf - that one - - just loose all the weight humanly possible .

Well, I'm not really worried about flight performance as the kit was designed, but rather the looks. To me the kit seems to be out of proportion just a bit, the fuse is too short for the wingspan (again just for looks).

I think if I get this kit, I'll just build it according to the manufacturer and ignore that nagging voice in my head telling me its too short!