Hi Steve, no doubt some people can get good results with A-series lenses, but in general I believe the 'official line', based on the Pentax Flash Manuals and the various discussions and testing that was carried out after my Flash Guide was released, was that P-TTL depended on the contacts, AF point and subject distance information introduced with the KAF mount.... so F-series types are the earliest lenses that are compatible.
Thats an 'official line' .... although maybe there can't even be an 'official line'
. Lets face it, a number of us were having to make it up as we went along, considering the extreme lack of technical data and official information published at the times of the various technology updates (eg KAF, F series, FA series, KAF2, P-TTL).
Anyway, for someone who's having concerns with P-TTL exposure, I think it would be safer to stick to autofocus, at least until things are working reliably.