Great looking smoker CARBON. If you want to expeiment with the slot idea, cover the top and bottom of the holes with tape. Yours would be easy with all your holes in a row like that. Or a piece of cereal box with a slot cut in it taped over the holes and you can change the slot size easily. If you don't like it, take it off. No harm, no foul.
Can anyone think of a reason not to use hinges as grill supports? Earlier in this thread someone used SS boat hinges that had a rotation stop built into them. He mounted them with the hinge pin horisontal so that the top half was either hinged up--flat against the side of the drum, or hinged down--90 degree from the drum wall making a shelf for the grate to sit on. This is a great idea, but the SS boat hinges are very pricey and I didn't see too many used in later posts.
However, a house door hinge--closet, front/rear door--mounted with the hinge pin vertical--just like in your house. They will fold to the side of the drum or to the center for grill support. They can be bolted or welded. They can be bought or picked up for free if you look for them. They will each hold 50 pounds. They won't fall back down while trying to put the grate or fire basket in place like the boat hinge.
I can not think of a reason NOT to use them. Tell me what you think.