the flare is controlled by this orifice yes... I never experienced a flare with this orifice...
What type of kickdown lever ratio do you have? How many springs did you install in the front clutch retainer?
I usually use a 3.8 or 4.2 kickdown lever ratio and install 10 or all 15 springs plus the orifice or a self made 1/8" NPT orifice with the same hole. Till now it worked pretty well.
But the good thing: it shouldn't harm the transmission to much. The front band just releases to early before the front clutches can apply. Usually it's the contrary on the 727/904, that's also not good for the trans.

Since you probably don't wanna reopen the trans and change springs or kickdown levers the easiest thing would be to increase the orifice size. It's a trial and error to get the perfect size. But since you only have a small flare you probably will have to increase the hole 1 time and then you will have a perfect shifting trans!