Rear springs: I currently have 7J0511115D which is 1 grey dot (0YA) weight range 1 and have some replacement rear springs which are 7J0511115F, 3 grey dots (0YC) weight range 3 for my T32 SWB which has been converted and therefore heavier in the rear. Am I correct that F (3 dots) would be a better spring as a result (heavier load) than the 1 grey dotted originals?