When I shoot 70-200 f/2.8 & SpiderPro, I have put the plate with the pin on the body rather than the collar. This is because I have a monopod plate on the collar. At first I was unsure but I've been using it like this for years now with no problems on 1-Series & 5D Series bodies.
If you put the pin on the correct side of the plate, the body and lens will hang correctly from the holster. It's all on the SpiderPro website user guide tutorials.