Just to close this out.
I tried a couple of dummy rounds to setup the dies & the idea of using a "spare" resizing die as a taper crimp type of die was pretty impractical once I set it up.
There is no way you can back off the die enough to get a consistent crimp with a definitive stop. What you have to do is back off about 3/4 of the thread length to get camming action from the press then just "feel" how much of the case is entering the die & being reformed. I didn't feel there was any way of being consistant in doing so.
Contact with Lee brings up the fact that the profile of the inside of the crimping insert in the FCD's has a shallower, longer taper before transitioning to the roll crimp part of the die. This is why threy are saying you can be less dependant on case length, but only in reality for taper crimping I guess. Supposedly they switched all their dies to this new profile at some point & its only an improvment if you have dies with the earlier internal profile.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”