Stalker used BSA and Daystate rifles as a base for many of his products but Bowket also produced handmade actions for some of the range. Leopard, Lynx, Bobcat, big bore Pumas etc. The 50 ft/lbs version of the Leopard was popular in Japan apparently Most were FAC versions he told me so it might be wise to contact him as he would know the best dimensions for a transfer port suitable for your Stalker. Have a look on the Facebook JB Fanpage for piccies of some.