Is the Super X Winchester a straight walled hull for this load?

Is the Super X the same as a Chedite hull?

Yes the same should have the separate plastic base wad .

Honestly , at that pressure , I don't think it would matter which hull you put in. Unless you want low pressure , then I would stick with the straight walled hulls.

Good luck finding the DR 16 wad, there was a fire or something at the factory, and seem to be out of stock from my sources, but they are working on it. I am out of them

I use RST Cheddite Hulls with SG-17 wads, 7/8 load and 19.0 grains of Universal powder. Velosity should be about 1125 with PSI of about 7,000. I've found this load with # 7 shoot to be very effective on Pheasant and Sharptail over pointing dogs.

SG-16 Wads
Poor typing on my part

7/8 oz shot is great in several gauges

16 ga. doves and ducks
 

Now that I've had a chance to do more than just shoot a few at the chrony, I'd like to share what's working well for me. I pirated one of these from Harry Collins (Thanks, Harry) and the other is nearly identical, just keeps the Bird Sheriff away from my duck blind. Have used 2 different wads, The Claybuster seems to give me slightly better 6 pt. crimps.
Cheddite or RST hulls - 2 1/2"
#209 Cheddite or #616 Fioche primer
15.7 gr. International
Sporting 16 wad
7/8 oz. #7 lead
Avg. 1133 FPS
I substitute a CB0100-16 wad and 7/8 oz. Bismuth #5 for ducks. Both give a soft recoil and fill my bag. I HAVE NOT HAD EITHER TESTED!!!

Based on the loads in that range that I've had tested you should be plenty safe and at something under 9K psi. Nice loads!

Edit to say they are most likely <8K psi and maybe under 7K. I shouldn't speculate tho. The load I was comparing to (in my head) used the smaller Remington hull which generates somewhat higher pressure than the more spacious Cheddite hulls.

Carry on!