Progressive Reg 412's 11" are naturally more stiff than the HD 12" stock but IMO the improved looks overcome the increase in stiffness. If you keep em on the lowest setting the increase in stiffness is relatively mild, but if you are a fat a$$ then you may bottom out on the lowest setting and will need to adjust to the more stiff mid or high settings.

I've had 412's for 3 years with no issues and would not go back to stock.

 

A couple or three guys on here have blown out the standard duty 412s.But none have blown the seals on the heavy dutys. The heavy dutys are for carrying 250lbs or more the ride is stiff but when adjusted correctly they will not bottom out.