Thanks for the tips!
However, I guess even with MDF there will always be some movement with humidity. Not so much with aluminum.
It's not just humidity. Even if you have constant, unchanging humidity it would still be a problem. You would also have to have constant temperature. Aluminum has a much greater expansion/contraction ratio than granite also. But at "normal" tempertures it is not a problem. Wood can grow/ shrink as much as 1/16-1/8" in a span as small as two feet between 32 and 120 degrees depending on wood type. Then there is swelling due to humidity/dampness. MDF is probably less, but then again it is formed under pressure, and it's made of wood. Toss a piece of particle board in water overnite and see what happens. 1/2" can become 1 1/2" thick as those sawust particles remember the size they were before getting crushed by boocoo tons/sq inch :!: The change in "typical" granite between those temperatures is a few microns over the same span, and is not influenced by water at liquid temperatures. But water that gets in granite's fissures and freezes eventually turns granite into sand:!: Remember that the next time you go to the beach.... And don't put a granite countertop on you barbeque island if you live in Alaska...............
There is a lot more involved with stoneworking than most would imagine. Seems like all the various materials have their pros and cons. What works with wood........what works with metals..........what works with stone.......what works with composites,resins, plastics etc...........all very different. There are also many commonalities too. Knowing a material's properties are key for purposes of application/suitability.
My purpose here is nothing more than a FYI..........for those interested. Has next to nothing to do with a Telecaster, or guitar building either.But then again, many problems with guitar necks/frets are a direct result of "properties".The musicality(resonance)/workability/price/profitability/beauty/tradition (not necessarily that order) of wood superceeds it's shortcomings, or something else would be used.