No.4 MkI barrel to channel contact when trigger guard tightened down.

[Towarzysz_Beagle]

I gather there is a collar in where the trigger guard screw front (Think thats the terminology PL uses) goes through as you have not mentioned it.

Yes it's there, and it seems to be functioning as intended (eg. Not standing proud and the trigger guard is applying pressure to the wood not the collar).