As far as a taper crimp not giving suitable tension to get slower powders, I don't get it. With slower powders than are listed for 10mm you're going to run into case capacity issues, and compressing the powder. What velocity / bullet weight are you trying to launch that's beyond the published 1170+ fps loads for 200 grain bullets? 

Try 14.5 #9/180gr bullet--that should turn your crank--& a good taper crimp.

my 454 Casull die is a taper crimp and have never had issues. My 475 Linebaugh is a roll crimp and again never had issues.

again it it the amount of crimp applied, I would suggest a separate
crimp die. 4 dies instead of 3.

Not a fan of Lee dies and don't recommend the, However thier crimp die is great. Have one for most pistol ammo I load.