Its not about solely increasing the port diameter or decreasing it, its all related to the static compression which dictates where the piston will bounce on the shot cycle.

Going to 4mm on a 35 being honest will border or slammy UNLESS you lighten the piston,when you lighten the piston you need less static compression to cushion the piston at the end of the shot cycle. Its still way to large imo, its better to reduce the swept volume to 39cc or so and cure the leaky breech and retain the 2.8mm port.

The 35 is not an efficient design though...it can be made to shoot nice however.