Personally I dont like any battery tube that is a neat fit for the battery to be installed. I have seen very slight lumps in the anodizing on the inside of the battery tube that has torn the heat shrink on batterys. The only reason they did not short was because of the anodizing that caused the tear in the first place.
Most Convoy lights, large or small, I purchase now I either ream or machine the battery tubes out to a bigger diameter.
Another reason batterys can be a tight fit half way down is that the battery tubes in two sections can have the threads machined of square. When the battery tubes are screwed together they end up with a bend at the intersection. This again has happened with Convoy battery tubes.
Not knocking Convoy itself as I like them, just pointing out some short comings that are not readily evident.