Sorry I missed your mention of reloading 16's. When I first started reloading Cheddite hulls, I also tried using the Claybuster 7/8 oz wad. I gave up because, like you, I found that it left too much space in the hull. Could not get them to crimp properly. I'm currently using the Claybuster wad in black Remington hulls. Works very well. I think quite a few of us solved the Cheddite hull problem without using filler, spacer, or anything like that by switching to the Downrange DR16 wad. Unfortunately, good luck getting your hands on any DR16's now. You'll likely have to resort to some sort of filler, as suggested above, if you want to use the Claybuster wad in Cheddite hulls.
