I can not emphasize enough how much I recommend that other RV-12 owners that do the spring upgrade, not follow this advice.
As has been discussed in other threads (and confirmed by others that have done the spring change), the amount of play in the fit of the arm to the shaft is well beyond the fineness level that we are adjusting when doing a carb. sync.
Flying for extended periods of time with the carbs even just a bit out of sync is the perfect way to spend a bunch of money on gear box repairs.
During carb removal for service/inspection, professional shops remove the arms from carbs all the time to avoid redoing the coarse set-up of the throttle cables but they always redo the carb sync using gauges afterwards.