As noted in previous replies, try it both upright and inverted and see if it's stable either way. if not it's not really a big deal, just find the point where it balances level for a moment or two and where it's just as likely to tip either way.
I never get too excited about precise CG position. For the maiden if in doubt err toward slight nose heaviness then you make your fine adjustment based on how it flies. After all it's how it flies that's important rather than replicating the CG position advised in the manual to the last millimetre.