My opinion only — Based on website data, 5250W / 240V = 21.9A. I would use the L14-30 wiring devices to not restrict capacity of the generator circuit. As far as the genset internal jumper—If the building neutral is bonded to ground {say, at the utility-meter/service-disconnect enclosure} and the neutral conductor in the building is unswitched, then the generator is not a separately-derived system, and the internal N-G jumper in the genset would seem to be a code violation.
Aside — Skim through this material…the mutant 6-20 cord-cap ‘3-wire to 4-wire’ L14-20/L14-30 connector-body bit is downright bizarre:
http://www.nooutage.com/mod6-20p.htm http://www.nooutage.com/images/Col-fax2.gif
