I am a little confused , as usual. Are you saying you have built many switch barrel guns off Remington actions? I had the impression that unless they were pinned so as to establish a fixed headspace which could then be duplicated ,at least by the same gunsmith, that rebarreling on a Remington would require headspacing for each individual barrel using a recoil lug of variable thickness.I thought that if an aftermarket barrel came up for a Remington action ,that I could not rely on screwing that barrel on with the recoil lug from that action .
I have 4 guns built off of trued Remington actions and they all shoot very well.
However , one of the main reasons that I love my Pandas and Vipers is that if I see a barrel listed for sale for a Panda,or Grizzly II, or Kodiak, or Viper, assuming the bolt face is the same, with certain exceptions, I can screw it right on , bore sight and start shooting . I can change barrels and be shooting in 5 minutes . I think this is one of the most valuable aspects of the aftermarket actions.