Thank you to all whom responded and shared ideas. I wanted to share an update to this one.
Ultimately I had to stop using my truck bed cover as a rest. It worked fine for <40fpe, but anything over that there were just too many moving parts, including the bedcover flexing up and down due to recoil.
The Caldwell Precision Turret, is functional, but far from "precise." The adjustable grip support is a joke, it is flimsy, too flexible. Adding sandbags helps keep the rest steady under recoil when shooting above 40fpe or so. The vise portion works well, I typically clamp the front of the pressure tube and rest the butt on a sandbag.
I do plan to build/buy some form of adjustable rear rest at some point in the near future.
After a bit of research I stumbled across something from Steven/AVS slugs. Some time ago Steven shared a video of using a miter saw stand as the base for creating a shooting bench. I liked his concept and made a few changes. I always needed a miter saw stand but never justified buying one until now.
I ordered a Wen miter saw stand from Home depot and used odds and ends I already had "in stock." The leg extensions are 24" galvanized legs used on commercial stainless steel tables. They are a perfect fit inside of the Wen stand's legs. The only permanent modification to the miter stand itself was drilling the through hole in each leg for the 2" snap pins. The leg extensions are drilled every 4 inches, height adjusts approx 32-48" or so, I've never measured it. Each leg has an adjustable foot for leveling. The current height setting is perfect for both shooting and miter sawing, for someone of similar size as myself, just over 6' tall.
The top itself is still a work in process, its shape has changed a bit since the above photo. I keep a sheet or 2 of OSB around for various reasons so I just glued 2 layers together. I may keep the OSB and cover it with 2 part epoxy. The top is easily removed with 4 thumbscrews.
This all prompted me to create a new 100 yard shooting lane so I can shoot from inside my shop.
I also picked up one of these hi/low shooting tables from MTN Caseguard. It is very lightweight, easy to transport/setup. Surprisingly stable for something so lightweight. It is very functional, I can see it being used for various activities other than shooting.