Transom talk

OK, I've just reached a major mile stone in my Osprey build. I am DONE planking both layers of ply. So I've started thinking a bit more about my final transom configuration. I'm clueless about the mechanical aspects of boat building so I'm constantly asking these sort of questions. Here are the facts. My final transom true vertical height is 19". That's measured not at the angle of the transom but the height per use of balanced level. As I recall, a long shaft is recommended for transoms 19"-22". With that said I think I can get away without using a jack plate (for now) Later on I might opt for an Atlas micro jacker or a Jacked up jackplate if I can find one at a reasonable price. So, Since I'm going to go without a jack plate for now I'll have to add an opening where my deck meets my transom (What is that opening called....brain fart moment). What is the minimum width and depth that I should go with for the opening? AND...should I really hold off on the jackplate? Is it a hassle to add one later? Although I'm not 100% keen on the opening I guess it would be nice since it will make access to my bilge a lot easier and makes mounting and checking my filter alot easier!

 

Lol, yeah...splash well. That,s what i ment. I,m pretty sure im going to get a 4 stroke 25 or a etec 25. Merc is at the top of my list.