I'm curious about the mission; ultralight, motor glider, ... ?
The ultimate target would be a sub 70kg ultralight (uk unregulated) but it might not add up weight wise. It will remain the target: 70kg empty, 20kts stall. Would be specified to a mtow of 315kg from a loads perspective so it can be flown as an SSDR microlight regardless of meeting the 70kg target or not.
Mission is maximum off-airport fun at minimum cost in a 3 axis machine, in a neat and easily stored package that can be kept in a garage and trailered easily.