I've asked for this before but it may have gotten lost.
On the boat menu screen can you add a 'select all' button. Clicking this would put all the up/down arrows in sync so that you'd just have to change 1 unit to change the boat for the entire stack.
It's a real pain (and time consuming) to move stacks of 8 onto a port and then have to manually click twice on every unit (requiring 16 clicks) to get the best boat. Even clicking once on every unit (8 clicks) to get the medium boat is a real pain.
KGB