Hi there, we do have a guide for Z fins and other brands, looks like the website has a glitch in showing it. Acc to the file I got from Z-Fins, the 7.7/115 works best with 37-38cm, which is what I use myself, mainly in SL, I´m 78kg´s and fairly experienced slalom sailor, choppier conditions in south africa or Lake Garda - I like the 38 in lighter winds, the 36 with a 7.0....37 is a bit in-between. SLM is def better in chop they say, but you need to be powered up. The SL is just a safe bet for most conditions.
I think generally lighter people may prefer the SL in fact, as most people sail a bit underpowered vs the pro riders. SLM seems best for overpowered sailing and to get over the chop, so I guess it depends on your sailing level, how "big" you go when choosing sail size vs wind? will get that fin chart up asap!