Polyester is the wrong choice imo for stock work. it shrinks, is weak, and is not very tolerant to the types of chemicals firearms are typically exposed to/cleaned with.
Epoxy is a much better choice from my experience.
As for making this work. When it comes to stock work we are about as fearless as they come. I've been able to build some rather strange/odd combinations and find a way to make it work and resemble a finished piece once completed.
So, with that being said it sounds like you have a McMillan setup for a heavy barreled magnum and your looking to squash a short actioned/light barreled receiver in it.
We can do this no problem. It's just a matter of you wanting it. Our rates aren't overly expensive, nor are they cheap. The labor is what it is and we try to offer the biggest bang for the buck whenever possible.
In your case it would be roughly equivalent to buying a brand new stock from Mcmillan that's been inletted already. What I can assure you is there's no one in this trade inletting/bedding the way we do it. None that I'm aware of anyway. The action is fully CAD modeled and then the stock is surface machined to emulate the footprint the parts will reside in. This gives a uniform/concentric layer of bedding between stock/action.
Does it make the gun shoot any better than a gun bedded by any other competent smith?
No, it doesn't.
Does it look/perform better?
I leave beauty to the beholder looking at it. As far as durability, I offer an unconditional life time warranty on bedding jobs. I've yet to honor it. We've never had a failure to date. They don't chip apart or flake off either. There's reasons why and it is what lead me down this route of cnc inletting the stocks.
We are very loaded up right now with work due to the new machines arriving and being setup. This will be our first full week back to work so we gotta dig out of this hole a bit. I've got barreled actions coming out of my ears right now.
I'd be glad to speak with you, but phones are especially tough to keep up with right now due to this hole I've put myself in. If you can sit on it a bit maybe give me another week to get some momentum on this stuff.
All the best,
Chad