You would have to try it. It sounds like you don't fasten the Homasote down since you take it on/off. In that case, the part not overhanging can flex up a bit when there is weight on the overhanging part. Try it using a suitable weight. I do think that over time the Homasote will give - you might have to overhang a different end each time. If it were mine, I would laminate the whole Homasote piece with 1/4" ply to give it some strength.
Brendan