Thanks for the replies.
The load I am using now is.. 2 3/4" Cheddite hull
209 Cheddite primer
19.9 gr. Hodgdon Universal Clays
Claybuster CB0078-16 wad
1 oz. lead shot
I had been using the Claybuster CB0100-16 wad that is called for in a 1 oz. load, but the crimps were unusable,
they were sunken in and the shot was running out. The wad I'm using now, Claybuster CB0078-16 is supposed to be used in 7/8 oz. loads,
but it makes the 1 oz. loads usable, but far from perfect. ( the CB0078-16 wad has a little nub in the bottom of the shot cup)
The 16 ga. Claybuster wads load best in the small capacity hulls like Remington and old compression-formed Winchesters. With the mismatched diameters you will eventually get powder migration and bloopers. The stack height is also bad as you've learned. I wonder how they come up with these loads.
If you're staying with the Cheddite hulls, I'd pick up the Gualandi (Ballistic Products "Sporting 16") or the B&P wad (Z16 or "Field Commander"). Another wad, the DR-16 (Down Range Wads) make up nice 7/8 oz. loads in a large hull like the Cheddite or Federal. The DR-16's have been tough to get lately.
If you have Remington or old CF Winchesters hulls the Claybuster wads work out fine. I like the CB0078-16 wads in Remington hulls for 7/8 oz. target loads.