Someone did a built up drum, I'm trying to remember who, Stumpy Nubs maybe? As I recall he cut a stack of MDF cookies with a 4-1/8" hole saw glued them all together with a threaded rod and then pulled the rod and put it in the lathe between centers and trued it up down to about 4" diameter. Actually, if you're worried about flex but not about weight you could fill the tube with Quickcrete but it isn't really necessary. Others have made these and as was said earlier just do light passes and at the low cost of PVC pipe you can make several and outfit them with with different grits and quickly change them out. Having been in the machine trade the suggestion to use the table with paper attached is really a good one because then the two parts are trued to each other. It also would be best if the adjustment could be made with a single control or the two could be locked together with either a chain drive or segmented belt drive. Single would be better always adhering to the KISS principle. I'm definitely downloading this and building it. Oh, as regarding kickback, not really an issue. You're going to bog down the machine before you get that far. The workpiece would have to have quite a taper to it before it would be able to get that much of a grip. Besides, with too heavy of a feed you're going to burn and ruin your workpiece and load up your belt in a very short time. It's sanding not sawmilling!