Way tooooo much!

Maybe you should change your username to Tommybullet.

I would follow 8178's advice on this one. If you do decide to use the .91, be sure to do some throttle management, specially on dives, as that setup has "flutter" written all over it. Worst case scenario, you could see the airframe fail right before your eyes (less likely). I'm assuming that the Kwik was built a long time ago and stored, and that you're dusting it off.

If what you mean is that you have an old kit that you're going to build, then think of the extra stress the .91 is going to put the airframe through and reinforce it accordingly.

Good luck.