AEA Challenger - mod factory shroud for noise suppression?

[duerksenlu]

I recently picked up a used .357 AEA challenger 24” shrouded barrel bullpup (bolt action, not the side lever).  When it arrived I was pleasantly surprised to see it has the plenum/regulator kit!  However, this pushes the fill port/gage a good 1/2” to 5/8” beyond the end of the shroud (see attached pic). 

I could get something like A Donny FL Ronin but as far as I can estimate I’d have to have a custom adapter made since the m18 AEA adapter has a flange that is too narrow to put the moderator past the fill gage (I think even a 1.5” diameter moderator would be up against the gage if using the AEA adapter…. really needs about another inch of material in the flange area to extend the base where the moderator threads on/seats, if that makes sense).

Has anyone come across this before?  What’s the solution?

Can the factory shroud system be modded for better noise suppression?  It’s currently about 115-120 decibels at my ear (using my phone app)….would like it under 100 if possible (right now probably need hearing protection if using for more than a shot or two).

Open to some ideas on this.  Thanks!