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 .