Roy,
I have the .15 size with a .32sx on it w/tuned pipe. Super fast. I did have to re-inforce the wing a little. I lost the wing on the first one. Also I moved the firewall back just over a 1/4". And back by the tall, I put 5/16 balsa inside the framed area for more support. It flies great. Just make sure you have dual rates set up so you can use full elevator upon landing. On my last one, I also sheeted the whole wing. I never weighed it, but it seems all right at the current weight. I have had 4 shrikes now. Two still flying. The other one has a .25 in it. I don't fly it much because it's boring after flying the other one. The one with the .32 will take off out of my hand at about 1/2 throttle. One other thing I do is angle the fins in instead of out. Just my preference.
Good Luck!
Craig
Craig's Shrike