I'm building one around a Rice .60 cal. Early Dutch profile barrel. At 41", it's a tad shorter than the original, but thats okay. I'm forging my own hardware for it too. The triggerguard (on the original) is unique in that the tang screw threads into a rearward return on the bow instead of into a separate trigger plate. The forward finial may have been forge welded to the front of the bow. That's what Ian concluded after examining it closely.
Art Riser posted pictures of Ian's rifle on the Contemporary Blog several years ago. Here are a couple pictures I saved from the Blog (photo credits Ian Pratt and Art Riser).