Well, talked to Polaris. Basically , it was a "use at your own risk" response for the 9300 in a vinyl lined pool.
I'm exchanging it for a Blue Diamond. Today is the last day for a mfg. $75 rebate.
I was wondering the same thing about a vinyl liner. Is it safe to use? I have a thicker liner (27 mil), and just ordered the 9300xi, but now am having second thoughts.