Hi Kumin,
We're in Washington county Maryland, near Harpers Ferry West Virginia. We hardly ever have any cold damage on Poncirus, but I haven't been able to keep any F1 types alive outdoors here.
I was a member of the Indoor Citrus and Rare Fruit Society back in the 80's, and my membership transferred to California Rare Fruit Growers afterwards, so I recognized Major Collins name when you mentioned him. The trifoliate I used on my potted calamondin is a descendant from the indoor citrus society seed bank offerings.
I'll keep your advice in mind when I order seed soon, but I have to operate within my Christmas money budget.
I hadn't mentioned it but I'm also trying to simultaneously improve trifoliate without citrus interbreeding. So far, I've got about a dozen zygotic seedlings of Flying Dragon lined out to see how much variation the fruit will show. I plan on extending that row as I germinate more seedlings. I've got another small batch germinating right now. Nucellar seedlings will become rootstocks; zygotic seedlings will get added to the row.
Thanks for inspiring the rest of us dreamers.
Tom