Nice idea. Should look a lot nicer then doors. Are you going to just put metal plates that over hang a little bit in the stand for the magnets?
Get us a pick of that part when you get there.
As far as the 40 gallon for the fuge, I gave 40 bucks for that one, if you want to pay that for it, or if you have something to tade. normally I wouldn't part with it, but my new tank is going to start being set up mid summer at best, next year at worse. And you are already at the point you need it, so it's only reasonable to help you keep going forward.
I also have the 50 or 55 gallon acrylic fuge that came out from under that 300 gallon. Would take some work to make it work.