Stumbled across the video of an utra-light with enclosed cockpit & nice looking airplane powered by two cycle or four cycle engines. Thought it was neat to see an airplane powered with a Briggs & Stratton 22HP lawnmower engine. The SD-1 has an ultimate G loading of +7 & -5 with and operation range of +4 & -2 G's, if I read their website correctly. The gross weight of this aircraft is 533lbs with an empty weight of 245lbs. It can be powered with engines weighing weight up to 89lbs including the four cycle 1/2 VW engines up to 45HP. They use a ballistic parachute, too.
This airplane does not fit within FAA part 103 Ultra Light rules, but fits within FAA LSA rules.
Burt Rutan designed the fiberglass "Quickie" canard design around the 18HP Onan engine, but in the end most people wanted more power.
Just found it interesting to see what people are doing with "very" light aircraft: