DUBIOUS
Following a PAPI below 300 feet from the threshold elevation may or may not be dubious to some, however the really important information to the pilot is the IVSI rate of descent which can vary depending upon actual groundspeed on the day but is TYPICALLY about 700 fpm for most jets.If this is monitored and adhered to it is very likely that you will arrive just above the correct touchdown point in the "zone" so to speak and what happens next is dependent upon your flare technique, another issue altogether.Chasing the PAPI below 2-300 agl is not a good idea in most cases.I have conducted 100s of hours of base training in the real jet airplane and this mirrors what we have previously practiced in the SIM and it seems to work quite nicely in general..........