RE: Where to mount the engine?
Before you even think about mounting the engine, you need to get the hull completed except for the deck. You also need to get your running gear, fuel tanks, cowlings, wings, tails and radio for one simple reason-THE BOAT NEEDS TO BE BALANCED!!!!!!!!!!!!!!!
Once you have everything, mount the strut, rudder and skid fin to the hull, lay the driveline in the boat from the engine to the transom, then EXPERIMENT with the radio, fuel tanks and engine locations until you get the boat fairly well balanced. You need to install your tail mounts at this time or earlier depending on what you plan on using to mount them. Something else you might consider is mounting your engine through the bottom of the hull. If you get four of the rubber inserts used in some of the engine mounts, fasten them down with screws through the bottom and mount your engine mounts on top of them, makes moving an engine easier later if needed. Here's some pictures of some of my boats, if they give you any ideas on what you need to do along the way. Just so you know, the cowling on that one boat is not the right one, That is a 90-94 Bud cowl on a 91-2006 Miss Madison/Oberto