MDF Rack dampening question

I've got a Billy Baggs rack of similar construction and I find thick maple platforms contribute very positively to better sound. Not all components respond equally well to sitting on maple, but that's true of every audio proposition. MDF is a dull sounding poor excuse for shelving IMO. Manufacturers use it because it's cheap and performs reasonably well, pure and simple. Better sounding shelving and speaker construction panels cost a lot more than mdf. I also find Golden Sound ceramic cones between gear and mdf shelving are a good thing. I'm sure there are many other good choices. You just have to find what sort of sound you like. Galen Carol Audio's website has a good summary of the sound characteristics of various footers & cones which I've found accurate. If you want to spend more, Neuance, Gingko, and others make good isolation platforms. Basically, the money you save on a less expensive rack with MDF shelving forces you to spend more money to correct the crummy sound of MDF. Think carefully about filing the rack with lead shot or putting spikes on it if you ever want to move it to change equipment, clean, etc. Your idea to use damping material on the bottom of the shelving will help to ameliorate vibration, but it will still sound dull and lifeless.