I would use a small about of epoxy to reinforce the firewall joints. You'll need taller main gear (CF is a good option for weight reduction -
http://www.tntlandinggear.com/store/...nding_gear.htm) to fit an 18" prop and everyone is upgrading their tailwheel to a Sullivan. I've heard the 1.80 runs really rough as well, so a vibra-damp mout or at least some rubber washers is probably a good idea (
http://www.dbproducts.com/).
Just keep the prop pitch 6 and under and watch the throttle on downlines. I think you'll be very happy with the 1.80. I wouldn't probably gone that route had I not found a 1.50 for a good price on Ebay.