Ever been on a ramp that's not steep enough? I have, it sucks. The opposite is true too. One that's too steep ranks high on the suck chart also. I have ramps I won't use due to not being steep enough or being too steep. Ramps are also affected by water level. My favorite ramp at our local lake sucks in the spring when water levels are high.

Buck

It's been a while since I've done a brake job on a late model vehicle but it used to be that the parking break was a secondary system which didn't use the primary drums or pads. Wonder how difficult it would be to rig a line-lock system for all four brakes.

Easiest solution is to have someone stay in the vehicle and on the brakes.

My last boat was a Monterey 218 LS, not a crazy heavy boat by any means. I was launching on Lake Travis with a friend's 2WD Expedition because my truck was in the shop and the ramp was slick. I was backing up and it pulled the truck all the way down the ramp. I am so glad I was dead on the right spot because there was another boat next to me. It did stop when the boat hit the water though. Very puckering experience. Never launching a boat with a 2WD again.

My 6 speed ram always made me nervous at the ramp.

If the ramps are not steep you would have to drive your truck into the water to float your boat. By me we have a 6' tide change and at low tide I still get a little wet trying to float onto the trailer. Not to mention what where the slippery stuff is on the ramp. Very easy to slide back. You can't just nail it you would just slide back into the drink

I won't speak for the member who had his rig slide in at Haulover in Miami, but I can tell you I slid myself in on that ramp. It is slippery as all heck at low tide.
I was winching the boat on to the trailer, stepped off the trailer in about 6-8" of water and it was like stepping on ice. In my flip flops, I literally just slid down the ramp like I was sliding down an ice covered hill. I tried to stop myself, turn around and ended up right on my butt. I could not for the life of me walk up the ramp and actually had to crawl my way along the trailer to get out. It would have been easier to swim to the pier ladder and get out!
Needless to say my crew and a few others got quite the laugh!