My first boat was a Lund 1650 Fisherman that I used to tourney fish back in the 90's. A 16 footer can 100% pop a 60" shaft out of the water in rough water.
There is a window where it's rough enough that you can still fish with enough thrust if you can keep the motor planted, but you can't if the motor keeps bobbing in and out of the water. On Slave Lake these days were quite common.
Does the OP want to drive 3-4 hours to a lake only to find he can't fish effectively because his motor keeps popping out of the water and he can't control his boat, so he has to settle for anchoring (you'll bob up and down worse anchored BTW) and catching fewer fish? I wouldn't.
Get the longest shaft and the most thrust you can afford. I run a 36v 101lb Terrova taken off my glass boat on my Lund SSV-16. It's awesome. Just the batteries in the bow alone changed it from riding like a tinner death trap to a fully-rigged dual console boat.