You'll need to take up cup space for sure.
There is no way to convert a 1 1/8 wad to 1oz without a bad crimp.
Try hand loading one. 16 grains is less volume than 16.2
Then you are trying to use a wad with a shorter base, and deeper cup.
If you get proper wad pressure, you'll have a 1/4" void at the top.
You should go to your gun club on their busiest weekday morning and trade wads with somebody.
We have guys fixated on economy that buy 7/8, and 1 oz 12ga wads by the 10's of thousands.
Perhaps your club does as well.
