I'm running a 25 inch shaft on a 20 inch transom with a plate. I like it you can tuck the motor in father the boat come out of the hole faster and planes in a very short distance. I never ran it with out the plate. You can see the plate it's only 3 1/2 thick and rated for 300HP
http://www.wellcraftv20.com/gallery/..._0036_1?full=1