How much is too much dual quad

Figure approximately 1.5 x CFM of a single 4bbl on a street motor and almost 2 x CFM on a race motor looking for a performance improvement from proper single carb flow. A friend took a Strip Dominator and 750DP Holley off his healthy 340 Barracuda 4spd, replacing it with a tunnel ram and 2 x 450cfm tunnel ram Holleys. He promptly cost himself .5sec ET. He was trying to salvage the situation, and I was wanting to try a 750DP like he was running on his single setup, so I told him to sell the 450s and get another 750 to exactly match his and I'd buy it 100% if it didn't help. Yep, 1500cfm on that tunnel ram worked on the radical little 340, and he knocked a whole second off the 450s!! Who knows, it may have wanted only 1300, or maybe 1100cfm, but 450 x 2 (900) couldn't beat a single 750. Your results may vary. I have personally ran 2 x 660s on a 383 with magical results and 2 x 850s on a 471 to good result. In the future, I want 2 x 1150s on a 526" B1 tall deck. We will see!