Yeah thats what I had in mind as well. I was thinking of taking 4 ten foot peices of 4 or 6 inch pvc pipe. I would double two pipes together, side by side, for each ten foot section. I would bolt these together on the two sides and the bottom with some four hole strut brackets to make a 20 ft run... My problem is getting it to float. and stay stable. I was thinking of taking four innertubes, the tough rubber kind and tying two together. One on top of the other and laying flat. I would tie four to each ten foot section. That way it sits up in the water and won't sink down far when the board hits the rail.
Then to keep it somewhat stable I would drop an anchor at each end and tie the rail off to the ropes.
What did you have in mind with the drums?