I was wondering if the 3 1/4 dr load will be to strong for my new P shooter.

A Parker in good shape should handle 3 1/4 Dr pigeon loads with no problem. I don't consider myself a competitive pigeon shooter any longer, so I limit my abuse to trap loads.

I've been racking my brain since this thread started "Where did I read that article about pigeon shooting with a Parker DHE?"
Finally, arter skimming through a few of piles of DGJ I found it! In the Autumn 1993 issue beginning on page 82 is Don Whittaker's story of his European pigeon-shooting adventures of the early 1960's "Preparing for Europe". Early in his tour, after losing a few too many birds, he retired his Purdey for a Parker DHE that would shoot 86% patterns from both barrels. He mentions a couple of shells he used but never discussed how they were loaded even though he also mentions Bob Brister in the article. There are two not so good pictures of his Parker and it has a single trigger, a pistol grip and a BTFE but doesn't appear to have a ventilated rib. He has the safety taped forward and it looks like he may have taped a spacer pad to the side of the already wide "trap style" comb.

In any case, he doesn't mention any problems with the Parker after he retired the Purdey to "back-up".

Does anyone know if Don Whittaker is still with us?

I'm going to make an educated guess that in view of the fact that he shot a late Parker DHE configured as a trap gun (with the exception of a ventilated rib) that it was highly likely to be a 1 1/2 frame gun.