To do that, I'd be crimping just below the lower edge of the cannelure. [b\s that OK?[/b]
NO. Standard 38 special dies have a roll crimper built in. Without a cannelure for the crimp to "roll into" you won't get ANY crimp no matter what you do. Try it, you WILL end up with bulged cases.
A taper crimp die will also have a difficult time crimping on the full diameter portion of the side of the bullet on true jacketed bullets. The jacket is pretty tough, it might take a little crimp before AGAIN
bulging the case. Taper crimpers are made for plated or lead bullets, much softer material.
I'm not familiar with montana gold bullets, are they a plated bullet? If so, you're good to go with a proper taper crimp die made for .358 bullets.