In '07, I was on both TE and the 2500 in 2007 Challenge groups.
TE was my "primary".
My miles showed up in - and counted toward totals in - both group lists. I'm not sure what I did that may have been different, but there's gotta be something in "manage my clubs" or preferences that you can select to ensure your miles count for both.
That said, I'm only in TE this year, and I am dutifully loggin' those miles!