Yah looking at the Allenflight extended tips on the Sonex.I think you follow most logical way.
If is request for demo aircraft, than your choice - Sonex - makes sense.
You modified Xenos to eXenos = you can use a lot of experience you already learned
Maybe you can ask producer for "small" modification and get "a little bit longer wings"
Of course not Xenos wings.... but even for example 30 ft span instead of 22 ft span will help.