A friend of mine converted the Circus Circus to a gas runner with success. He used a standard 1 1/8 Speedmaster rudder, (go dual pickup if you can) and a 1/4 round bottom hydro strut (not extended). He used a Dick Tyndal (Virgina Craftsman) turn fin. He runs a stock Zen 26 with a 90 deg header and tuned pipe. He used a 8 or 10 oz tank converted for gas, but I'm sure a bag would work as well. You can use a standard zenoah mount, you may have to get smaller iso rubbers (see the McMaster/Carr part number in the Warpath instructions). He did not move the motor, its mounted as far forward in the engine compartment as it will allow. The starter is almost against the cowl. His prop has been a Prather 265 or 270 on a 1/4 shaft. he did have to cut the bottom out to get the mounts in, and then re-epoxy the windows he created back in. It runs strong like this, its light. It will carry the right sponson down the straight, and require a little left input to go straight as well. I wouldnt put anything modified in it, You'll spend more time rowing out to get it than running it. If you want to see how it runs, check my review of the Hitech Sport Hydro, the second boat is this one.