Interesting on the climbing the glass . . .If you use glass a fish tank stick a line of clear packing tape all the way around the inside of the tank about 3 to 4 inches above where the top of the feed will be.
The glass is just rough enough that after a bit of dust gets on the glass the beetles will start trying to climb out. Kind of like a fly walking on the windows. The tape is slick enough that the beetles will fall back down. You will have to replace the tape every once in a while.
Don't try to fill the tank up with feed. Having the feed over a couple inches deep keeps too much moisture inside the grain and the next thing you know you have a tank full of mites. Horrid things. An inch to a inch and a half of feed works best.
DO you think the 2 inches is better because of the depth of the tank -- it not having the same circulation of air that a flatter , say 6 inch, container would have?