One of the 300 Savages I load for is a Savage 99. It has an old Weaver 4 power scope on it and is in decent condition. I'm loading the Sierra 125gr #2120 bullet. It sits on top of IMR 4320 powder but I have had good groups from IMR 4064 as well. With bullet velocity at about 2700'ps, the old gun will shoot 1" groups all day long. Might give that a try. I doubt slowing it down is going to effect stability any. You might play with the OAL in 10 thousandths increments but I doubt you'll find a sweet spot- the bullet is just too long.
Just a hint. Obviously I don't know your experience in reloading but on the old guns, I start and load 80% of max load listed. Then I dial in accuracy with OAL. Works on the old guns. Since I'm old too, I'm not a player for most of the new and improved cartridges that don't do a darn thing the old ones aren't already doing. But some sound intriguing, like the 30 TC but frankly, it's just a 300 Savage in disguise.
I think the old Savage round is grossly overlooked these days. I'd love to find a Remington Classic in one with the 1:10" twist. I'd be hard on the coyotes with the 125 gr TNT Speers. Considering the round is just behind the 308 but much less recoil, great accuracy, what's not to like. But I guess since the word "magnum" isn't in the name it will stay in obscurity. Best of luck with your project.