Anyone done one, can one of the aftermarket 700 bolt releases be fitted?

I use BAT or Stolle bolt releases in XP-100 actions.
I have had several spring loaded "Pull Out" versions come through over the years.

The Witchita is nice as well.

NO, 700 or Seven bolt releases will NOT interchange to a 600/660/XP-100 s/shot.

XP-100 s/shot trigger group is attached to a slotted recoil lug w/ a transfer bar attached to a sear housing w/ a torsion spring counterweight pinned into the stock to assist transfer bar reset.

Copy the HS Precision variant by adding a slotted 1/4" diameter stud attached to the aft end of the OEM bolt stop w/ a hole in the stock.

The receiver/Sinclair spring loaded type are FUGLY.

A XP-100R is basically a Model Seven action w/a 3rd pin & coil spring for bolt stop(aka 722/721).