Sorry, I'm coming very late to this thread, but it seems like the right place to post.
I have been vacillating over which hitch to get for our 2020 Chevy 3500HD CC 6'9" bed and 2020 (ordered) 310GK. I have looked at both the Demco and PullRite auto sliders, both of which (currently) require an ISR adapter plate. And, of course, they both need capture plates on the MorRyde pin box, as well. I'd also need a crane to get them in and out of the truck bed. So I'm not too crazy about the auto slider option.
I measured the position of the pucks/gooseball mount, and it turns out the pucks are 3.35" aft of being centered on the rear axle, and the gooseball mount is 4.5" aft. That makes the Andersen Ultimate and the Demco Recon, both of which mount to the gooseball, pretty attractive, since (if I'm doing the math correctly), the turn clearance on these would be >90 deg on the Andersen (regardless of coupler block orientation), and ~86 deg on the Demco. They're both fairly easy to move around, too!
The B&W Companion (non-slider) for 2020 GM pucks is currently only shown as appropriate for long beds, but I don't know why, unless Chevy uses a different puck layout for the different bed lengths (could that be?). That hitch would also provide good turn clearance, I'm reckoning ~83 deg. I can't imagine needing more than that, but I'm sure that there are people with dinged up front caps and cab backs that said the same thing...
There must be other SB hitch options out there. I'm not looking very seriously at manual sliders due to having to rely on my vigilance in moving them when I should. I wanted to post what I'd determined for any others of us who have the 2020 GM short beds, with the new puck pattern which is not widely supported yet. I'd be delighted to hear from anyone who's had the opportunity to try a hitch on the new GM short bed.
Don