I had an '86 Holiday Rambler, 33', And with everything rebuilt it was tough stopping it. The only thing that helped was a brake buddy in my tow car (a Saturn). Make sure the fluid in the hydro boost master cylinder is clean and full. The master cylinder for the HB was located to the rear of the entry steps on my rig-- it was a chore to add fluid to the cylinder because it was mounted almost up against the floor. If I remember right it only affected the tag axle, which was a ford F-350 drum brake setup. The rest of the brake system was Chevy ( P-30, in my case).
Good luck, let us know about your results,
2002 Newmar Mountain Aire, 37' gas
2002 Newmar Mountain Aire, 37', 3778, W-22, 8.1 Vortac, Ultra Power upgrade, CAI (cold air intake), Taylor wires, colder plugs, Koni shocks.