I was able to make and use the TT-30 to 14-30 homemade adapter.
Yesterday evening when I was in the field I saw a graphic that had arrows drawn on it that fully laid out the project. That helped a lot. Can you repost that for my future reference? I saw that image using my smart phone yesterday. This morning, when I logged in to JA to make sure that I rated your assistance so you would get paid, the link to that image seems broken.
From the TT-30 pigtail I connected to the Leviton 14-30/50 plug. I connected the green wire to the ground pin, black to one of the thick flat pins, and white to the "L" shaped neutral pin.
I worked perfectly just like that. I didn't even put the second flat pin (for a second hot) into the 14-30/50 Leviton plug. So it's working with only those three pins sticking out of the plug.
I did test the outlet with my multimeter and it was 120 v, not 240.
And the 50 amp cord that you posted will work when I come across 50 amp power on the pole, which they have this year I've found. Two years ago they didn't have the 14-50 receptacles at all the camp sites, some only had the 14-30.
Thank you again for your diagram, time and effort.