I am going order that probably next month, and based on weight will use or MVVS 61 or 77 if that closer to 6lb, think that may be good enough, if that closer to 8lb may be YS 110.
Meaning 3D flight, as far as my knowledge, most expensive for engine is hover – where only weight is considered not length or wind span.
I think if You have 91 that is not a problem with over power it self, just do not user full throttle, problem with over weight on nose that may give a problem with balance.
A little extra weight on the plane with 1027 sq in should not be a problem, only balance.
If I’ll get more information from hobby people I’ll keep You informed.