Looks pretty cool and the plastic covered magnet is a great idea. Thow if the silicone is the only thing that is holding the magnet in the wood i would pull it out and use some thing else to hold it in there. Silicone doesn't stick to wood very good at all. They do how ever make the aquarium putty that works greats on wood and rocks for reef and all i have used a ton of times with great succes. [ http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=3962
Were did you pick up the plastic covered magnets? I can think of a few different applications that they would come in handy for my self