Don't have a good answer for this. Trapdoor hammer is pretty slow as is. Maybe reduce hammer fall. Not a simple matter with an original tumbler hardness. Weaken main spring? Width first, maybe slightly thickness, almost guaranteed to ruin it. Seem to remember someone was selling short throw, two notch tumblers (full cock to open action, which bothers me), but don't have a name.
Chuck

Way to lighten the US Springfield main spring is to reduce the width of the spring. Little at a time grinding.  Buy a couple of replacements, it's trial and error and you will over grind at least one.

My advice is leave the issue tumbler sear trigger relationship alone.  Make all changes with reduced spring tension.  Never saw a good job changing issue set up other than the springs.

Problem with switch barrel or liners rim to center is the Rim fire does not want a lot of hammer, Center fire needs a lot of hammer.  My Switch barrel CPA's run a fairly light hammer spring for the Rim Fire. CF use pistol primers,  Remingtons will pop with Rim Fire hammer tension some other brands won't

You might have to come up with the same compromise for the switched Trapdoor. If not it's fairly easy to switch Trapdoor main springs. One for CF one for RF  Get the Arsenal issue take down tool for spring switching. Easy gun show find.

Boats