You can use letter size drill bits and what they call a "pin vise" to carefully hand drill out the nozzles. As for overall volume, I believe the only way to increase it is to have the linkage in the proper hole (closest to the pump) and have it bent so the plunger is topped out. As with any carb, remember that as you go bigger with the squirter size, the duration of the squirt will be reduced because the overall volume is dumped faster. But I don't believe you have to go too big on the primary squirters because the bores are so small. Lot's of other adjustments can be done with the secondary air door and linkages to minimize flat spots or bogging. (I'm still learning.)