Nice review, as always JW. The BB is a really nice shaft too, both performance and cosmetics wise.
I finally got to see the 913s this past weekend at the Golf Tour Trailer at Westfields GC here in VA, didn't get to hit them though. To me, in terms of footprint, the D2 is a little more rounded and almost symetrical compared with the D3, which is your traditional pear-shaped head with more of a bulge/bias towards the toe. I didn't think to put them side by side, but it's a very subtle difference, which is confirmed by your pics. Anyway, the D2 seems to frame the ball better for me, since I'm used to the more triangular, symmetrically shaped heads. Can't wait to go back and hit them both.
Oh, and they had these lofts for both D2 and D3, not that I could ever hit one. Maybe with a high launch high spin shaft, LOL.
Sorry, I shall not digress further, don't mean to take anything away from this thread.
Cobra Fly Z 9.5*, Fujikura Speeder TS 6.2
Callaway BB 816 15*, Fujikura Speeder TS 8.2
Adams XTD Ti 20*, Fubuki AX h500
Cobra Fly Z+ 4-PW, KBS
Vokey 250.08, 254.10, PM Grind 60*
Ping 1966 TR Anser 2