Here some good infos=http://www.boatmad.com/forum/f5/outboard-height-pic-requests-24901.html
I've installed a 6 inches jack plate on a Solent 750/300 vmax a couple of years ago, and put the engine at down position ventilation plate Vmax 8cm above the hull bottom, the engine was centered on the transom. for an overall use, this is good.
be careful if you're using a front steering to allow enough space for tilting the engine inside, sometime using a jack plate and front steering it can be necessary to increase the space above the transom. See last picture.