Need some help assembling rear shocks on US. As per diagram, I have new cartridge screwed into leg eye. Do not have part#31 41 20054236 "shock absorber protection casing" (not listed for US ?). Have 3 stop rings. Have nut on cartridge shaft which is shown on diagram but not listed in part numbers. Have part# 33 53 3054201 "stop plate" which has part# crossed out on diagram. Have "compensating bumper". I have run the nut to the end of the threads on the shaft, run the "stop plate" down to the nut, and installed the "compensating bumper" on the "stop plate". When I insert this assembly up through the mount hole in the frame(temporarily without spring), there does not seem to be many threads (5) available for the "cap" (soft aluminum) over the "rubber bumper" and "plate", to hold the the whole assembly against the spring pressure. Is this correct?