Of course, increasing RPM by a few can easily increase output by more than any porting changes could. We could measure volumetric efficiency and determine just how much improvement is possible. While not the same, Lycoming aircraft engines have similarly poor intake airflow setups. Yet, they operate with very good volumetric efficiency until max RPM of 2700.
Tuning the intake and exhaust with long tubes might provide some ram effect and raise the smoke limit a few watts.
Note: There are some tiny turbochargers Such as the VZ21, available on Ebay for about $110-140. They are absolutely tiny, and might be small enough to use on a 6/1. Maybe I'll purchase one...