Forgive me for rehashing an older thread.
I have Triple DCOE 40-151 on a Datsun and they only have 3 progression and a massive lean-spot with the throttle cracked.
I have researched endlessly and think that an additional progression hole would fix the problem. But then others say NO way, never touch the progression (yet they modify every other part of the jets and chokes and stuff).
This picture really highlights my issue. At 1000 rpm with everything dialed in and calibrated the butterfly is still way too far towards the engine to immediately expose the 1st progression hole when the throttle first moves.
Did you all have good experience adding additional progression holes?