I came across to this thread by googling the cart in question (PC-550/II), similar story to the OP.
I bought an astatic replacement stylus just to test it (without knowing the Jico SAS option), listened it very briefly at the time and back to the drawer it went
Just recently tested some carts of mine and included the PC-550/II in the test and was actually amazed by the sound of it even with the "unknown" stylus.
It however tracks quite lousy based on Hifi News test LP tracking test. It does not sound that bad at all and everything besides the tracking is quite spectacular. I'm wondering is it worth the Jico SAS stylus and has anyone tested this combination? I haven't found much comments on it around the web, is it just not that much appreciated, assuming that it is not that unusual cart to find in old Pioneers.