The RT-590 leg bolts are approximately 7/16 inch. The bracket body mount holes are 1/4 inch. So I had to ream out the top bracket hole to fit the leg bolt. On my two hole body mount bracket I only used the top hole. I was afraid to drill a new bottom hole in the grill body to fit the bottom bracket hole because the competition cart inner mount frame for the pellet body is real close to the lower bracket hole. RT only uses one body mount hole for their front folding shelf so I did too. It feels good and strong to me. I think the Amazon 12 inch bracket has three body mount holesThank you for the reply and pics. Your shelf looks awesome. We’re you able to use the existing holes to mount the brackets or did you have to drill new ones into the cart?