Looks amazing. I wouldn't be too concerned with your stand. I have the same filled with vinyl. Not sure how much but I know 1/3 of it lowered my already lowered car almost 2 inch in back and made my car virtually un-drivable. People uses these the time for records and they hold up to that.
I'm not too worried about it now. I ended up reinforcing it with 2x4s Still trying to figure out what I'm going to do about a door, though.