Sounds like you've already made up your mind, but here's another gas option. The SYSSA SAP-180 (30cc) is a great little motor with rear exhaust and rear carb...great for tight cowls. It's not as cheap as the Asian motors, but it's AMERICAN MADE and well supported. When comparing price, consider that the SYSSA comes with a rear exhaust pits muffler, ignition switch and stand-offs (in various lengths). Total engine weight is 40oz with muffler and ignition. I met Todd Syssa at Toldeo, very nice guy.

[link=http://www.syssaaircraft.com/]http://www.syssaaircraft.com/[/link]

There's also a very comprehensive thread on RCU here:

NEW SYSSA 30CC GASSER MADE IN THE USA
[link]http://www.rcuniverse.com/forum/m_8862472/anchors_8862472/mpage_1/key_/anchor/tm.htm#8862472[/link]