Ah, rimlocks... I'll have to deal with that issue - manana, maybe...

I used D606s on a couple of Husky 610Es, but found that open-road use with 26psi (rear) caused shedding of the centre knobs, which is a strange feeling. Lower pressure seemed to be ok, and the tyre would last about 4000km of varied use, including highway operation.

I guess what I'm saying is, that based on the above, I have found about 20psi works for me with knobbies. They usually have hard sidewalls, so with heavy-duty tubes 20 is plenty imo.