So, an out of date RAIM prediction says no, a more current one says yes, and there has not been a RAIM failure or warning, but you're going to turn around and go home if thats the only approach?
Why?
Is it an out of date prediction?
Company SOP's. Regs say RAIM must be available prior to descending below LSAT/MSA.
Its a bit like not tuning and testing a ground navaid just because it is not NOTAM'd as being unserviceable.