There could be a few issues going on. What is the temp in your house? My house gets very hot so when that happens, my Edgestar has to run constantly which can really bring the Rh down.
Read this great thread from Chas (who builds the shelves) who did an experiment on Rh and how he shows the Rh swings when the unit cools.
http://www.cigarasylum.com/vb/showthread.php?t=19092
Also, I would recommend getting more beads to help stabilize it. Technically 1lb might be enough based on the recommended calculations, but I would definitely get at least another half pound, but more like another full pound. You should also space out the beads... some on the bottom, some in the middle if you can and some on the top.