I think folded ports have been tried. I would expect the folded part would be resonant at a different frequency than the main part of the port. If I were to try that, I'd make the bend at a 45 degree angle so that neither half of the port reflects straight off of the corner. The 45 could be a great place to mount wheels for a large cab. If we follow this far enough, we could reinvent the PV 1820!