I have RCBS and Redding dies and I don't crimp even on the 300 WSM because the resizing/seating has always been enough to hold mine pretty tight.
7 Mag loads out similar to 30-06 for powder and I've never had any issues with it either. If this was a 375 or 416,458,460 Weatherby, then that crimp would really come into play,but with 7 RM it isn't as critical.
As per Redding instructions, if your bullet has no cannelure or crimping groove DO NOT attempt to crimp. That is because the brass case is softer than the copper jacket and you will have a tendency to deform the brass. That is why I don't crimp is that Accu-Bonds and many other bullets I've used don't have a groove, and even the Barnes TSXs I've used didn't have the rings line up, so I went with COL.
If you do have cannelure bullets then you can crimp by adjusting the seating plug depth to match the crimp ring on the bullet,tighten that down and then turn in the full die 1/4 turn (this is after you initial set-up of contact with the shell holder and going back one full turn!).
Then you can adjust your crimp more if you need to by more adjustment on the full die and readjusting the seating plug. A little trial and error with a dummy cartridge should get you there.
Again, the is NO NEED to crimp even with a 7 Mag, especially with a bullet with no groove, or even those that have one.
As for stability, I've never had any drift in my COLs once I'm set properly.

EDIT: Your COL is more important than the crimp, because if your crimp changes your COL proper depth then accuracy is effected.