I would go with a long shaft. whit a short shaft when you kick it in reverse it will hitt the back of the boat and not go anywhere. I have a 1675 lund explorer with a long shaft T8 (the best motor in my opinion by the way) and it works just fine. It dips into the water a little when I punch the gas but comes back out after I’m on plane. I had a 15hp short shaft on before that and had problems from the get-go.
I measured the transom last night and it is 15″ where the kicker will be mounted. I was ready to buy a long shaft and a dealer told me to go with a short shaft due to the short transom…