had a short shaft also,but
found that within a couple years the motor mount being lowered got water logged & had to remake the wood mount.Suggest if lowering the mount do the following. As you lower the mount use the old bottom holes for the new top holes. That way you only have to tap 2 new holes & fill 2 old holes. I simply plugged the old with caulk & stainless steel bolts & nuts. That way if I ever blew my engine & purchased a long shaft the conversion back was simple. Reinforce the 2 new holes as the stern wall in the new hole area is thinner than where the old holes were. Dismantle the wood mount, ream out the holes that are tapped through it slightly and put numerous coats of polyurethane all over, on, in & into the holes to totally seal the wood. It will save you having to rebuild the mount in a few years. Check it every year & add a few more coats.You will find that you will have to lean over quite far to start & operate the engine as it now sits much lower. A little inconvenient but not impossible.Good luck,PJ