Norma, within the general scheme of things, 6 minutes, in a Hobart, assuming you're going with a low setting, is relatively minimal kneading.
When I was kneading bromated All Trumps by hand, if I kneaded it 2 minutes, it was undermixed, but at 3 minutes it was too much and the dough would end up bucky and the crust tough. 2.5 minutes- perfect. You don't get much to play around with. You blink and the window passes. You won't get that with 12.5% protein flour. With 12.5, it's not like "Oh, my goodness, how can I hit this target?" It's more like "Wow, this target's big"
With bromated 14% you have to catch it on the way up to peak gluten development, whereas, with 12.5%, you can hit that peak development plateau and spend a considerable amount of time there before the gluten starts breaking down.
Assuming this is a production setting and an overnight ferment, I'd try 5 minutes first and then 4. Don't be afraid if the dough isn't smooth- it'll be smooth by the time you form it.