Temporary (!) ways to disconnect the surge brake on my 1992 Cobra:

1. The aft end of the long brake rod under the trailer (just ahead of the axle) is threaded and attaches to the "splitter" plate that pulls the Bowden cables, one for each brake. IIRC, there's a nut and a lock nut: just remove these and pulling on the brake rod will have no effect on the brakes. Make sure the aft end of the brake rod can't fall down and drag if the emergency brake is actuated. If so, cable tie it to the bracket under the trailer.

2. Recently I disassembled the front pivot for the hook that is pushed by the end of the surge brake tube inside the tongue. That hook then pulls the brake rod, which runs under the trailer. On my trailer, remove one bolt and the hook and emergency brake assembly fall out. You could just tie up the front end of the brake rod and the emergency brake handle and mechanism with a shock cord. Fold the handle down before you do this, though. This would disconnect the brake but it might also allow the sliding tongue to compress even more than normal when braking. I don't think so--there's an internal stop--but I'm not going to try this until I check.

3. The ends of the Bowden cable housings bolt into the splitter plate. So if you unthread the cable housings, the cables can't be actuated. If they're flopping around loose, tie them up so they can't drag.

Methods 1 and 3 involve crawling under the trailer. It's not bad; you don't have to jack it up. Method 1 is quicker and easier. But method 2 would be easier still if it doesn't cause harm.

And, of course, you have to be careful when reassembling that you don't thread things up too tight and actuate the Bowden cables, then drive around with the brakes partially applied. In my experience, it's very easy to see when the cables are slack and when they're under tension.

Of course, a brake system that works every time would eliminate the need for any of this.

Chip Bearden