I have the Manners stock for the 455 VPT (no cheek rest) with two sling studs, and installed the Area 419 weighted arca rail. The rail is 14” long so it’ll extends a little out past the end of the forearm. I was able to line up one of the sling stud holes with one of the mounting holes in the rail but had to drill and insert 2 T-nuts further back on the stock (I wanted 3 mounting screws).
The rail comes with three T-nuts and three threaded bolts. Installation is pretty easy if you have the basic tools. Area 419 has a video that covers the install. You just need a drill, drill bit (can’t remember the size but may have been 1/4”), and a 3/4” spade bit for the countersink for the T-nut. Easy job, maybe 10 minutes. Don’t breath the saw dust!