Richard,
The MDS came from my local hobby shop. It was $109 from them although I think the price has come down. I have a Bisson Muffler on it, run a 16x8 APC prop (have tried 16x10 APC and a 17x10 Mejzlik but the 16x8 seems to work best) and run Omega 10% with some extra castor thrown in for lube. An Enya number 3 plug (expensive but well worth it) and lastly, an ASP1.08 carb ($35 from Horizon) as the original made the engine run like crap. The ASP carb turned a boat anchor into an engine with probably 8 or 9 gallons thru it that I can hand start. I have no experience with the new carbs that MDS puts out although they are supposed to have solved the mixture problems now.

For the price, the engine is hard to beat.

Check my gallery for a couple of shots of the Ultimate.