If those balls are as big as they look (24" on the outside perimeter) then its more then 150lbs. Its your space so what you say goes. If you want to be nice about it you offer for it to be certified.
Right now I'm in a working theory of doing a layer of black, seal it, then doing another layer of layer. The tape seems to have a lot harder time breaking through the sealer to raw wood.
That article is very old and the ingredients have since been changed. It won't leave any grease (its actually what I use to clean grease off of steel) and all bricks will eventually get a surface rust to them due to the nature of raw steel.
Seems to me you would be a pretty good candidate for the Warped tour. They seem fine to take reasonable untrained people on the road with them. Pay isn't that good but if you just want to get out there for the party then thats the place.
Diablo 60 teeth blades in table and chop saws does a good job getting through most anything. Try to get something in the high 80s to 100s with as small as kern as possible for doing plastic. Also try to find someone that can sharpen blades in your area. You wont believe the kind of money it will...
Norcostco does sell a per assembled package for pneumatic casters. A little on the pricey side but the tutorial does a great job of explaining things. Automation direct usually has the best prices on any pneumatic cylinders.
The designer might want to make sure its legal to have plexi as a boxing ring under the governing body. I would think they would be pretty picky about the surface there fighting on.