Put it on the front plate and take it off the back. Technically frames are illegal in TX anyway, but cops don't care if it's only in front. Honestly most don't care about either, but there is the occasional nazi, or longhorn/aggie/rice fan.
The $30 fee that the alumni site charges is for the physical plate itself. There are no other reoccurring fees outside the regular DMV registration charges.
The funny thing is, despite the obvious LSU plate I already have, I have only gotten the finger once. It was from a Rice chick, and I think we had just knocked them out of the CWS. People here are either too nice or afraid I might be one of the gotti boys...