say if im going to put an MG hole on the mantlet of the HL Snow Leopard, does someone who already did this have the right diameter,distance from top(mantlet),from side (mantlet),etc to make it more accurate.

because if one make a mistake on drilling one the nasty Hole cant be undone. or youll'e gonna have to repair it with something to fill it.

Tried to look at the real pershings to be a refference, but its hard to compare a photo on a front,side,views from an actual.