Koji noted oddities in the sensing matrix results I had gotten; namely that the plots showed REFL33 not changing at all, when we know for a fact that this should not be the case.
Gabriele lent his eyes to my code, and came up with the idea that the modulation depths I was using were maybe not ideal (.1 for both 11 and 55). This affects REFL33 in that it is not simply Carrier * 33Mhz + 11Mhz * -22Mhz but also 22MHz * 55MHz, etc.
I got more realistic values from Jenne (0.19 for 11MHz and .26 for 55Mhz) and re-ran the code, with more realistic results. The behavior for 165 has remained the same, but the other signals are more well behaved.
Moral of the story: the modulation depths affect the 3f signals in a complicated way.