Hi all; I have picked up an old B66XL, to complement my "color B66XL" with colour diffuser head. I have a few questions on the B66 head; 1) how should the condensers be set? I note that they slide in and out; and there are multiple "slots" for them; 2) If I get some Multigrade filters; how do I put them into this beast? 3) Is there a need for head-absorbing glass? if so, where does it go in this head? I'm putting a darkroom back together; thought the condenser head might be fun to experiment with; it has been decades and decades since I used a condenser head (and, quite a few years since I did any darkroom work; so this is a fun project) Thanks; JohnS, Ottawa.