Tom,
Hi!
Unique is one of our staples, but we tend to use it more in handgun loads than anything else.
For whatever reason, it really is hard to find data for reduced loads. I seem to recall an article in Wolfe's Handloader in the area of 10 years ago on reduced shotshell loads. I have also read articles on reduced loads in Handloaders Digest or Gun Digest, but probably 15 + years ago. Also An NRA publication discussed them, also about 15-20 years ago. I actually cannot recall other treatments of the issue.
Your ideas of shortening the shells or using filler/OP wads under the combination wad and shot protector sounds as if it should work.
We have a couple of Dillon 550B loaders. They work well and load very rapidly. For whatever reason, I think I am happiest using them to load straight handgun cartridges (using carbide sizers of course). Everything slows down when we go to bottlenecked rifle cartridges. I have even considered shifting back to my old Lyman All American Turret Press to get a more hands on feel. I'm not sure I get that much speed from the Dillons with the bottlenecks. However the Dillon's additional leverage is really appreciated when resizing bottlenecked brass.
I can commiserate with you on getting too busy and lazy to reload. The main area where we cannot get good factory ammo is medium powered ammunition, especially for magnum handguns. I have yet to find a good factory medium powered .357 Mag. load. I'm not happy with factory ammo in .32 H&R Mag. either. And we won't even talk about factory ammo in .45 Colt. I have a reduced recoil 12 ga. short magnum load using Blue Dot. It does seem to work well. I got it out of an NRA or Digest article about 15-20 years ago. Incidentally if you need it, I actually have a shot at locating the NRA/Digest article of 15-20 yrs ago since I used one of the loads. Come to think of it I read another article on reduced shotshell loads for beginners about 5 years ago in one of the above publication, but I don't know which. At least modern data is out there.
Some friends have a daughter who is an Olympic shotgun shooter (3-time medalist now). She typically shoots over 3000 rounds a week. Before she became prominent, her father was handloading all her ammo!!! Needless to say he likes high volume equipment.
Good luck with the load development and gun.
John