To be honest I got sidetracked by your comment about your student pilot friend who flew off a Phase I in a Sonerai but personally I would say a Sport Pilot flying off a Phase I would be solely dependent on his experience and skill level. For example, if he was say 100-150 hr SP and had no spin training I would say not only no but hell no.
But this would also apply to ANYONE flight testing ANY new aircraft of ANY kind!
Mel, DAR since the Last Century, Specializing in Light-Sport and Experimental Aircraft. Certificated over 1,100 Light-Sport & Experimental aircraft.