The 444 Marlin is a nice round, but it is not something that I would personally use in a Siamese Mauser action. The Siamese Mauser is much bigger and it is a reputably strong action. I have a lovely 45-70 custom heavy barreled Siamese Mauser gifted to me by Huvius. The actions that I have look capable of taking even bigger rounds. That's why this speculation . . .

I have also received some excellent advice from Master Gunsmith and forum member Steve Zihn. Hope to decide soon.

Thank you, everyone, and do keep the advice coming. Nothing is more delightful than the decision process leading to getting a gun built.

Good hunting, everyone!