Ah yes, your the one with the fully stripped interior.
I think the difference in feel for the ARB is to do with the difference between the 172 and the 182 Cup suspension. From what I understand the 182 Cup suspension is stiffer than the 172 (as a passenger a Cup packed 182 certainly 'feels' stiffer). It therefore wouldn't surprise me to find that you had to set the ARB to hard on a 172 to get the same feeling as you would using the soft setting on a 182 Cup.
I'm taking my spanners to Bedford at the weekend, I will do a back to back test and see.