Did you try just removing the secondary air door all together ? Its surprising how there is no bog without an accel pump in the back.
Least on my dual quad I got rid off the front carb air door and lighten up the rear carb door quite a bit. No bog and hits harder then any 750 Holley carb I used
Guys used to remove the air door on single carb set ups all the time. If the motor has a high stall converter and loose gears, should work just fine. You can move the accel pump rod to another hole to give a longer shot of fuel if need be