you want to mount the screen where you can see it while fishing, so if you fish from the front of the boat most of the time, then mount the screen up front. You can mount the ducer to the TM whether you mount the TM on the front or the back depending on your circumstances, how you fish, etc., or mount the ducer to the hull. if you fish around stumps and such, there is always that possiblity of damage, but its just part of the game. The only way to avoid that is a shoot thru the hull ducer, but they don't work well on tin boats, only glass. You want to rig the boat up where everything you use for your style of fishing is close at hand for convenience, there is really no "wrong way" to do it, it all depends on how you want it set up for you.
GO BIG ORANGE !
I meant to behave, but there were just way too many other options available at the time.