On my Kadet Sr I extended my wing by 1 bay on each side and it just added to the floating effect the wing had.
The LT-40 balances on the main spar. If you put the balance of the wing in the same position as the LT-25 the throws will probably will need to be reduced because of the shorter moment between the wing and the stabilizer. The tail control surfaces will become more sensitive. I would suggest that you balance it a little bit nose heavy, perhaps mounting the servos last to set your balance point. By that I mean after the plane is completely built including covering, fuel tank, engine, batteries, because the covering on the fuse behind the wing will affect the balance. Have it ready to fly except the servo position. Make a servo tray that will mount on 1/4 inch squares attached to the sides of the fuselage. Adjust the balance by moving the tray for best balance before the first flight. This way the plane shouldn't need any additional excess weight to balance it. After that use the batteries to refine the balance to your way of flying if necessary. Trainers give you the best point for the model to fly best. Other planes give a range to adjust the balance so it can be tailored to your flying style. Keep in mind , there is a saying, a tail heavy plane flies once, a nose heavy plane lives to fly another day. Good Luck with your project
