i know u r supposed to gap the plugs smaller when running lpg
1.0 -1.1 petrol
0.8 - 0.9 lpg

will having plugs gapped 0.8mm and using petrol have any adverse affects

Nah you'll bne fine.

IIRC I have mine gapped at 0.7mm to ensure there's no spark blowout with the supercharger - and it drives fine when off-boost.