Free: Contests & Raffles.
Good questions. I don't know all the answers, just know that lately I've mostly been using Warne 2 piece steel bases and they seem to work really well. I only went to a one piece base, a Warne aluminum picattiny rail, on my Rem. 700 338 Win. Mag., only so that I could mount the scope further back for proper eye relief.
I’ll ad that imo if you are thinking that an aluminum pic rail or steel for that matter will add rigidity to an action you are worrying about the wrong things. It’s still held on by a few small screws.
I've always used two piece bases on everything from rimfires to 30 calibers magnums. I torque the bases and ring screws to the recommended settings, don't use loctite or other fastening compounds and have never had a problem.