I have a 4.5" no name manual JP on there now. Pro V 150. I looked thru all of the performance info on here and came to a conclusion. I cant pinpoint which amount of setback I need. The 6 or 8" will probably get the nod. Does the extra 2" make that much of a difference as far as setback? I understand the JP concept, but deciding which one will be difficult. (BTW If any of y'all have one for sale , manual. .LMK) thanks.