If you can't stop your trailer at 10mph, it shouldn't be on the road.

That I agree with, but only a split second as you said.

Did you say trailer is a 1989?
Maybe it needs a master cylinder.

Master cyl was replaced during the disc brake conversion with a disc type master cyl abt 5 years ago.

Trailer stops from 10 MPH. It was running 10 MPH below the 55 MPH speed limit going down a steep hill and around a corner where I was concerned abt it not stopping in time.

I found a thread on this site where a member was having the violent brake shudder issue. He had a buddy drive the tow vehicle while he rode in a different vehicle next to the trailer and saw the front axle tires lock and release rapidly causing the tires to repeatedly hop abt an inch off the ground then it occurred. When the snubbers were examined, they had little to no resistance. Snubbers were replaced and issue went away.

I sent an email to Myco support. Awaiting a reply..

IF… boat and trailer 5-6k and brakes only on one axle, after several panic stops on test drive I would expect temp to be over 160. If your sure there is no air, is base brake system good? Pads wearing even? Slides free? Pistons move freely? Calipers on correctly?(bleeder at top)
I don’t know, but do stainless rotors require a specific type pad?

I believe boat is 6800 lbs dry + alum Myco trailer, soo,,, ~9000 lbs as it sits??
Master cyl feels firm when actuated via the breakaway lever w/cheater pipe..
Brake rotors/pads look new. Sliders are sliding. Pistons not sticking and bleeder is up.
Purchased the drum/disc conversion new as a kit so pads should be the right ones. Don't think SS rotors need special pads, but never had to replace them.

Got to thinking abt the reverse solenoid and wondering if it may have something to do with what I'm seeing. I know what it does, but not sure exactly how it works. Need to dig into that next.

I know for a fact that I wasn't able to back it into the shop (slightly uphill) w/o the trailer wiring plugged into the truck in prev years, so guess I could try that "test".

It energizes and stops flow from master cylinder from the reverse light circuit so that you can back up. A line lock in essence.
If it is energized all the time, then yeah you'll have issues

I’m surprised a set up that heavy doesn’t have brakes on both axles and equally surprised the brakes aren’t getting hot.
Interesting thought on reverse solenoid though. Maybe leaking by solenoid or wiring issue on trailer getting feed back to it?

Just convert to electric over hydraulic and be happy with it. Surge brakes aren't worth the trouble anymore.

Think I found the issue.
I was using the breakaway lever to bleed the brakes just to be sure. Placed a section of square tubing over the breakaway lever for leverage. When acuuating the lever, it felt firm. However when I applied a bit more force, the lever moved considerably. Then noticed when I put the extra press on the lever, the master cyl moved aft a half inch or more.. Pulled the master cyl out and found its mounted to a spring loaded mechanism. After a certain amount of press is applied. The master cyl moves limiting the amount of brake press that can be obtained.

Now need to figure out what to do abt it. Wondering if the mechanism is sprung for drum brakes (that need less press than disc) to prevent wheel lockup??

Considering welding it together but still awaiting reply from Myco.

May have to. Dont really want spend the coin since it's not getting used much. Also want to see what can be done with what I have now.