Charlie- I did not know that, thanks!

Well, here's what the RS cal looks like:

20 Hz: add 7 dB
40 Hz: add 2.5 dB
80 dB: add 1.5 dB

So maybe the real answer is, start by adjusting so that you get "matched" (or referenced) levels with the RS meter, and then keeping in mind the numbers up above, adjust the subs level to taste.

The sub tone on the 950 and Avia, etc, is some sort of white noise compendium of more than 1 freq.