I too amp in the process of breaking out of an L5-30 to a distro.
My need stems from a way to get power from my two Honda eu3000is generators (L5-30 outlet) to the distro.
The distro has two L14-30 inlets with each inlet going to two 20 amp/breaker'd circuits.
Instead of changing the inlets on the distro to L5-30's I did the following:
Yesterday, I made two extension cord/adaptors.
30' of 10/3 SOOW cable w/ L5-30 male on one end and L14-30 female on the other end.
On the L14-30 female I put a "jumper" combining the X/Y terminals....very easy to do.
I tested it and it works well.
My need stems from a remote outdoor gig last April where the PA/stage ended up being under a tent due to inclement weather.
On that gig I was fortunate enough to be able put the genny on the down-wind side of the stage (approximately 20' away from the stage) using a 12 gauge extension cord.... It was a windy day, thus the exhaust fumes were purged/vented. If the sides were on the tent, I would have been in a bind.
The issue with that is the fact that I could only use 20 of the genny's available 23 amps.
Using my cords/adapters (going into both sides of my distro) I will now have all 23 amps available per generator/side of my distro (total of 46 if I use both gens).
Of course, is this UL approved (probably not) but it would get me through a "one off" if needed.