I hated those two bolts. Almost need to be an acrobat hanging upside down and skinned knuckles to get the bolts off to check and/or have it filled.
I replaced the two bolts with small safety clips. After using them for a couple of seasons I bought a gas fire ring. I bought a tray that holds 2 tanks with a spin down collar to hold them in place. I installed the Flame King tray with 2 u-bolts to hold it in place and no longer have to fiddle with those terrible bolt holes in the bottom.
You can put a single tank on the rack and store something else there or have the spot if you decide to carry a spare tank in the future.