you don't even have to have a hole in the butterfly at all.
Just want to set the record straight ... I am NOT modifying any throttle discs in any way, just installing the CORRECT Duraforce one with a 0.10" dia hole in it (98-7047). An incorect disc for R-Tek Snowthrowers was accidentally installed on many Duraforce Lawnmower carbs in 2002 and 2003 which has a 0.055" dia hole in it (Can't confirm Toro p/n since all R-Tek numbers have been converted to B&S numbers).I didn't say they would run better. That bleed hole size is going to change tune of the carb. Any change to it and you will have to make tuning changes.
Most everyone I've talked to settled in the size 40 pilot jet area with no mods to the throttle disk. If you had a bigger bleed hole in the throttle disk i would expect you to need the 42.5 pilot jet.
Did you ever run a size 40 pilot jet over the 37.5 with the original throttle disk?
Send yours my way. I have never had a minute's trouble with my 10424. The only complaint I have is that the handle adjustment doesn't go high enough for me.Wow. One more reason for me to stay away form DF's. I just dont like the buzzy handle feel. Maybe a Gold would set me okay....Im thinking about it.