Hey Homer,
Well, I just found this post, sorry I missed it a month or so ago.
Looks to me like your wire length is just a bit too long.
When I built my 3 element Quad I was able to get PHENOMINAL results from it by tuning it to a gnat's eyelash.
If you go back to the standard 75ohm transformer matching system, try wrapping the 75ohm section into a common-mode choke to help attenuate feedline radiation/coupling.
I simply cut my driven too long, then using a carefully cut 1/4 wave 75ohm transformer, cut the driven wire until it showed a flat swr on my chosen center frequency.
I then cut the reflector 6% larger than what I ended up with for driven wire length and began the process of cut-n-spin tuning.
I placed a vehicle several blocks down the street with an SSB rig locked on keydown on USB, and adjusted the carrier balance VR off slightly so I had about a 20-30 milliwatt carrier, giving me just enough signal for tuning.
I pointed it away from the 'beacon', checked the S-meter, then pointed it toward it and rechecked the S-meter.
Cut, recheck, spin 180*, cut, recheck, spin 180* etc...
I was tuning the reflector on ch.20 so I could pass it up enough to notice the slight drop in performance and found it dialed in on ch.34 as center, close enough to ch.37 where I was wanting it flat.
Then I added the director and repeated the painstaking process of cutting, rechecking, spinning, cutting rechecking, etc...
When I was done I had quite a performer.
I won't bore you with the entire story, but Clancey (R.I.P.) had an early '70s Hy-gain Long John 5 element Yagi on a 60' tower and a 150w pep.
I had the 3 element Quad at 52' boom height with an itty-bitty 80w pep amp.
He would often, and typically under the affluence of Inkahol, get belligerent with me regarding this, "POS wire antenna which couldn't work as well as a true horizontal Yagi because it had no elements in the true horizontal plane."
One evening, back in the early '90s, as I spun the dial I heard him in QSO with an Australia station. While he was keyed asking for a signal report I rudely keyed over him and threw out my call: 'Gold Coast 223'. Immediately the Aussie returned with, "Stand-by one, 223".
When Clancey unkeyed he received a good report: S-7 to S-9 with excellent audio, then the Aussie gave me a 20-over-9 report.
That was the last time I heard squat from Clancey about my inferior Quad beam.
