Well, advice is appreciated and I shall be additionally cautious. Incidentally I was well aware incidentally that aerobatics aren't advisable/allowed.
For a Cessna I was advised that a second or two of zero G with the power off was fine for the engine. I did them at 4000 feet so that if the engine did cut it would hopefully have enough time to draw the fuel back.
I can genuinely say that I've never pushed the spamcans I've flown beyond published limits of g, bank, speed etc... and left a good margin to boot.