I've been searching for hours and can't figure this out!

I need to layout two unique 4x6 postcards on an 8.5x11 sheet with different
text on the backside. Side 1 has a return address and the recipient address.
Side 2 has dear recipient first name and one or two unique merge fields along
with non-merged text and an image. I'm merging from Excel and each record is
on a single line. The final merged doc needs to be page 1 - the first two
postcards, page 2 - the back side of the first two postcards, page 3 - the
third and fourth postcards, page 4 - the back side of the third and fourth
postcards, etc. I can't get side 2 to populate from Excel. I thought about
just making two docs and print side one then side two on the backside, but I
need to duplex the print job so I can't.

Thanks for the help!
kj