I am a large rider ~300lbs. I have a Novarra Ponderosa with an aluminum seatpost. With about sixty miles so far, the bike seems to be holding up fine to my weight with one exception, the seatpost.

Shortly after I start riding the seatpost slides down about two inches or so. I have the clamp as tight as I am comfortable with. My idea is to machine a piece of aluminum tubing 27mm outside diameter with an inside diameter of 19mm and a length of approximate 210mm as a shim to prevent the seatpost from sliding below my preferred height.

Does anyone see a problem with this solution to the problem?