Adjustable needles are nice and a convenient way of adjusting the mixture..The range of movement is about 1/8 inch, but within that range you can zero in to a good mixture most of the time..
Once you drive for about 300-500 miles, if you pull the spark plugs you can evaluate the color and determine if the mixture needs adjustment. Then, even though it's not as convenient you may be able to alter the height of the fixed needle.
Loosen the set screw and pull the needle down to lean, or to enrichen, see if you have room to push the needle higher; if not shorten the needle carrier.
Just remember even with an adjustable needle set at the mid point of it's adjustment range of 1/8 inch, you only have 1/16" to play with.
About all I could suggest aside from what I already have is go thru the dripping carb as see if you did anything different. Make sure the choke's hollow disc has enough spring pressure behind it to keep it pressed against the body of the carb and there are no grooves that might be diverting the fuel into the starter box housing
AND if you put Grose jets instead of the original needle valves, replace the original needle valves unless you have reason to believe they were malfunctioning..Even if you replaced the old needle valves sometimes even the brand new needle valves stick open, so think about putting the old ones back
One last thought for tonight..make sure the dripping carb is not dominating.
Check the balance between the 2 carbs again.