Here is the deal on Progressive 440s:
For standard and tourer: Standard Rate is the 440-4213 (C for chrome/ B for black)
Heavy Duty is the 440-4221 (C or B)
For Interstate: there is only one shock recommended and it is the same shock called heavy duty for standard and tourer, 440-4221, BUT IT IS NOT IDENTIFIED AS A HEAVY DUTY SHOCK, IT IS CALLED STANDARD RATE FOR INTERSTATE, THERE IS NO HEAVY DUTY SHOCK MADE FOR INTERESTATE. This is just Progressive's semantics, but it has lead to a lot of confusion.
I had a long talk with a Progressive tech about the SuperValk with no trunk/back seat/sissy/or passenger ever, and SHE recommended that I use the 4213 at my 180-5lbs, which was my feeling as well (even though the SV still has the 7 gal tank and fairing). She explained that it takes 8 of 10 (available) turns on the 4213s to get the same suspension rate of a 4221 set to the cushiest setting.