Due to beautifull Irish summer I havn't had very much time flying mine to do to much acro stuff so I wouldn't know if yours is underpowered, sorry.

CG in mine is a little back 10 mm from recommended (98mm I think!)

My F3a flying friend reckons it's a bit forward for serious acrobatics at that.

Speaking of waiting for parts, where do you get yours from ?
Sorry if I'm being nosey