http://www.rcshowcase.com/html/engines/rcs400.html
20 lb, 23hp 400cc 5 clyinder radial.

This engine has got to be getting close to bridging the gap between
ultralight and RC (understanding it is expensive for an ultralight)

What could you do with this? twin engine PBY ultralight? (twin because,
reliability?)

the 215 cc verion gets 76 lbs of thrust (that info is not available for
this engine)