The key to making these fit between the runners was cutting off the VR38 mounting tabs. That being the case, I could likely still keep using the OEM VR38 stalks; thus reducing costs and also solve the spring-falling-out issue with the PRP stalks in one step. The coils would sit a bit further down between the runners, so the mounting solution would need to take that into account to keep them accessible.
I'll noodle on this some more, but this feels promising. I probably should have thought of that as I was doing the setup, but better late then never...