Erik,

You wont be dissapointed with ZDZ range of engines. I have the 40 RV upto the 210. I can't make comment on the kit you want to use, as I have no expience of it's construction. I do have a ZDZ40Rv in a 30% Cap 232 3D by Topmodels.CZ specifically designed for a gas motor.

I would recommend that the only type of firewall to use with a gas motor is made of aircraft quality ply (rock hard stuff). You can bolt the engine straight onto the firewall and not necessary to soft mount (this is a contentious issue with some!) but I and many of my friends have done this for years without any problems. I do recommend you use KS Krumschied silencer, wow the quality and performance is unbeatable!

You will need to beef up around the firewall, I use 1/2" hardwood around the rear of the firewall. You also need to pin the sides of the firewall with a good quality hardwood dowel or screws for extra support. You will need to cut a hole on the firewall approx 50mm dia for the carb to stick through. You then will need to see how your going to get at the mixture screws, normally an appropriate hole for a screwdriver to fit through. On my CAP I had to extend the firewall forward for the spinner/prop to match the front of the cowl with a box section and this made the carb be outside the fuselage (if you follow) and it was easy to set up the mixtures with the cowl off. You don't need the cowl on to set the mixture, as it won't change after you fit it. Tip keep the ignistion pack well away from any radio gear.

I hope this helps you, but word of warning. If the manufacturer says no to a gas motor, it's probably not strong enough in it's present specification, why did Chip say no?