let him crash it........there is nothing like a good trashed **insert expensive toy** ruined to inspire a little LISTENING.

Kinda like paintball guns....i told the kid running a high pressure regulator on a low pressure gun was a bad idea.....i told him, but he wanted the L33T thing....that was a neat way to do 300$ + damage to a gun. course the next one got a bath with liquid CO2 cause mom made him sell the nitro and other gun to pay for a new one(heres a hint, most electronic valved markers will not accept CO2 because the valve cant handle it going liquid as it decompresses).......

I know just enough about building them to wish you luck getting A. the wing apart, B. the retracts(wich are expensive btw) installed and the wing together structuraly sound, and C. keeping it in the air.

Have you stopped to consider, since your obviously interested in having it scale with retracts, that adding THAT much bigger motor is likely to require cutting the cowl open and a very un-scale cylinder head sticking out? why not go with a powerful( ie a jett or one of the hopped up os or other racing motors) .75 -.90(ie whatever will fit under the cowl and remain aas concealed as possible) and work on a tuned pipe with scale exhaust outlets.