When I got my grit guards and tried to put them in my green buckets from Menard's,
I found that they were sitting maybe 4" too high.
It sounds like this was the same size bucket as several others in this thread have found.
My solution: Stick your foot in there and step on that sucker until it sits on the bottom.
I recommend doing this before filling it with soap and water, but it probably doesn't matter.
Now my grit guards are stuck in my buckets and don't fall out when I dump the buckets out.
Why would I ever need to remove them anyway?
If just stepping on it hadn't worked, I next would have reached for the heat gun.
I think some of you may be over-thinking this.