Drilling out an RC carb is generally a bad idea.
One must keep the relationship between the throttle barrel opening and the opening in the carb body so that the closing point of the cab throat is not at the lower edge. You must insure that the spray bar sees negative pressure at all times. This cannot be accomplished (guaranteed) with a drill bit.

The power limitation of the LA engines is that the crankshaft is too small for any high airflow. This is from the outside diameter not allowing any dwell (time that the crankshaft is fully opened under the carb), to the fact that the crankshaft bore inside the crankshaft is too small. A tuned pipe is probably the best option to gaining power. Time the power peak for low rpms (10 to 12K rpm).

But there is little point in making a silk purse out of a sow’s ear.

Have fun,
Konrad