Four good chocks. I also have a set of wheel locks (police style tire boot) for security but they also will prevent the wheel from rolling.

Wheels chocks will work fine. I do it all the time with one or two on an incline like yours. (usally two) Electric brakes would work fine untill the battery gives out. Surge brakes might leak down. I would trust wheel chocks over trailer brakes any time. If you sleep better with a chock under each tire that is the way to go. One will hold it. Two is safe, Six is silly but better.

Ok - thanks for the feedback. Chocks it will be I had an medium set and just found a large set. I will do all 4 tires just to be safe. I asume I should let the trailer roll forward and get some presure on the chock before I un hook right ?

We had to swap trucks on a hill once. The tranny blew on the way up to Lake Winni in NH. It was a LONG azz hill so backing down was not an option as we were almost to the top. We put every bolder behind the tires that we could and prayed

Just run a chain thru 2 wheels as a backup to the chocks.

DAMN GOOD IDEA.

Some smarta$$ kid might kick your chocks out just to watch your boat crash thru the house across the street.