I struggle too. I thought if I crossed Nepal and Tommy Toe both round reds that I would get a round red. These are slightly ribbed and slightly flattened like Russian Reds.
No, I am not trying any F2's in the fall crop as I want to grow out about 8 plants to see what segregates. I will do this next spring.
I have 5 of my Brandywine X College Challengers in the greenhouse fall crop. I hope the cross took.