Motor bolt hole question

[3 Squids]

I'm reading in multiple places people talking about drilling oversize holes for mounting the motor to the transom and then coating the holes with west system to prevent any water that makes it pass the LifeCaulk from getting into the wood. Anyone done this? Wondering how much bigger of a hole. 1/2" bolts so 17/32 or maybe 9/16? I'd like to do this to the blue boat before I hang the motor which is going to happen very shortly.