Re: Platforms questions???
Adding my recent wisdom building a platform:
1. I agree with Scott that you should try to build a narrower wood center strip and wider "Drop zones" with the rubber. Apparently this is quite controversial, but I made mine with about a 3'3" center and basically 2 1/2' rubber drop zones on either side. Of course that means you'll have to buy more rubber, but it will potentially be easier on your equipment and you don't have to "aim" it as much when dropping.
2. I used scrap oak hardwood flooring in the middle and love it. The only modification was I had to sand off the original "pre-finish" with 60 grit sander then further sand across the grain with a belt sander, digging into the wood with the sander at an angle. Then I applied 2 coats of water-based poly (no preference to oil, it was handy). I think the poly takes away the grip, but if it's roughly sanded the surface is perfect, as far as I can see.