I gotcha about the fluid dynamics. That's why I say, test first before the mounting. With the tire off and wheel hub, you can observe the brakes in action after you tap in the surge brakes with the lines and a tee adapter. You will be able to physically see how much movement you get on the brake shoe and whether or not you get good contact. You will definitely need a full bottle or two of brake fluid, and need to bleed them, but those surge brakes can be worked by hand if in good condition and it should tell you everything you need to know. If I had welding skills, this is something I would have already done.
The size of the brakes will determine stopping power for the most part, provided the fluids are sufficient to force the brakes to close. My money is on the fact that they will. Good luck, and keep us posted. Perhaps someone has done it before and will enlighten us further. It sounds like a fantastic project and I for one, would love to know, so I'm sure there are tons of others too.
