I 've got auto on the CLK but it annoys me when the blower keeps changing speed, I know it's supposed to but, I have it on
manual and currently set at 22 deg, if it gets too warm I just knock it down a degree or two.
I removed the glovebox and the airbag to give more light on the subject, the worst bit for me, was adjusting the glovebox lid
after re-fitting to get it to latch properly both sides but, got there in the end but, I don't recall cutting any ducting.
You used to be able to get replacement bleed nipples with NRVs built in, as a direct replacement for the originals
but, I've not seen them anywhere for years.