Baby your boat
Tom: You are asking for opinions with your question, and here's mine:
I take my motor off and carry it in the Suburban. I wouldn't even think of leaving it on the motor bracket for more than just moving the boat around the boatyard. I baby my boat, but I have had it for 28 years and don't know when I'll buy another one. I actually only carry sails, life jackets, and fenders on my boat when I trailer it. When my boat was new, I had a metal gas can in it, which wore a spot in the liner near where the gas can sits, when I trailered it from Pennsylvania to the Florida Keys. Since then, I reevaluated what I keep in the boat when I trailer it, and baby it. Keeping the motor on the bracket would stress the hull and the bracket, and the motor mounting block, especially when the trailer hits bumps, or pot holes. Maybe this wouldn't hurt anything, but why risk it? It only takes a minute or two to put the motor back onto the block.
Aldo