I'm running solid flaps on mine and have won the Stock Class at the Tri-Power Nat's 5 times with two trips to the King of the Hill Race (last man standing).
The key is a combination of things, fuel "sloshing" up the rods from a standing start is something often missed by folks tuning these carbs.
Pull-off release time, flap tension, hanger height, taper and tip length of the metering rods, POE set-up, etc also play a role here.
On the later units you can also get fuel "slosh" from the vent behind the choke flap and vent holes over the POE wells on some airhorns.
When set correctly you should feel nothing put strong accelleration, no noticable "kick", or transition of any type when things are set correctly. That's the parts folks miss with these things, they expect to feel some sort of secondaries "kicking in", which happens with just about every type of aftermarket carb out there. When you feel anything other than getting planted HARD in the seat and strong/smooth power from idle to the shift point......you need to keep tuning because you just aren't there yet.......FWIW....