[flyingfrizzle]

If it is a floatation style bracket mount it low as possible and use the outboard holes for adjustment up or a small jack plate. You will want to get the most floatation out of the bracket you can on an 18. If it is just a standard style bracket that dose not have a large flotation chamber on it then going up an inch or two will make sure you don't run out of adjustment when you start to raise and adjust the outboard...