Without having a schematic on that particular model and LED specs (none available that I know of), increasing the drive on those LED’s would be risky.
The only safe way that I can think of is to remove the plastic lens plate that’s mounted in front of those LED’s, and try it that way. If you’re stratified with the improvement, replace the plate with a clear piece of plexiglass instead. The stock plates are usually colored, diffused or cloudy. They let you see only the LED segments, not the body of the LED or anything else surrounding them. I usually prefer the stock filter plates for that reason. Of course some filter plates are more transparent than others, but that filtering will cut down on the brightness and sharpness of the segments somewhat.