Me again! As Stefan stated, the SLS (Studio Loud Speaker) feeds are just that. They come out of N39 & 40, are 1/2 normalled down to P39 & 40, go to DL 33 and head off to the studio live area so the musicians can hear what they have just recorded on a set of speakers in that room. This was common practise years ago but I have a feeling that they are hardly used these days. Musicians have to take their headphones off to listen and would perhaps like to hear the takes over headphones or even in the control room as the monitors there would be better and more inspiring in a more acoustically controlled environment.
I don't own an SSL anymore so, I'm writing this stuff from memory but I have a feeling that the reason you can't find the LF and RF outputs is because your console is a 6K. These dealt with 3 x stereo busses, A, B and C for music, effects and dialogue plus a straight L & R stereo mix which seems hard to find so far! The 4K was a 'normal' recording studio console involving stereo and quad feeds (left and right, front and back) so, LF and RF may not existing on your console.
The centre section patchbay wires (rows L&M and N&P) should, I think, all be labelled so, if you see a wire idented as P39 on a DL (33 in this case), it originates from patchrow P, jack number 39. Wires from patchbay points which go to the 2 centre section 104 way 651 Mrac connectors will also be labelled with the patchrow jack point references.
Mini outputs: Your 6K may just have 1 set of mini outputs (L39 & 40). To listen to an alternative set of mini's, you wire the 2 wires out of DL 33 and into a relay box provided by you. The Alt button on the 651 is just a straight switch contact which you need to wire out to the relay box via DL 33 I think. Once pressed, it would trigger the relay to switch between the different sets of mini speakers connected to it. SSL later had mini 1 and 2 outputs without the need for a client supplied relay box but it seems like your console may not have this facility depending on its age.
Stereo distribution: SSL supplied 5 stereo outputs for mastering or client copies on patchrow L27-36 on the patch drawing I have here. These were linked (or probably fully normalled) from M7 & 8, the L & R programme outputs. I will look through the info I have here on the looming specs and post something on that later.
The trouble with this stereo distribution is that, once you connect an unbalanced machine (a cassette in the old days) into one of the 5 outputs, it unbalances all the others so, beware of that. Some studios sent the stereo signals to a separate distribution amp which then fed the various 2 track machines.
I would suggest having your DAW stereo inputs wired separately on the patch. That way, you can use the console L & R inserts to go into a compressor for instance, like you mentioned, and cross patched into your DAW bypassing the group sends/multi inputs patchrow, H1-48. Unless you rewire the patchbay a bit, which could easily be done, this would take up 6 additional patchcords as it involves 2 cords from the insert sends to the compressor or other device, 2 back from there to the console insert returns and 2 from the main L & R outputs into the DAW inputs.
Again, this is from memory so please correct me anyone if I've got my thoughts wrong on this. I'm from the old school before DAWS were invented so I am somewhat ignorant regarding this matter! Haven't DAWS got a set of stereo inputs?
Hope this helps (and I'm accurate with my information) and doesn't confuse you even more!