Doug,
I put some numbers into EZNEC, and came up with:

20 meter support dipole, 34.1 feet long at 40 feet.

40 meter inverted V hanging from 20 meter dipole, 66.7 feet total length,
with ends drooping down at 30 degrees.

SWR is less than 2:1 from 14.0 - 14.4, and 7.0 - 7.4.

Directivity is about 6db on 40m and 13 db on 20m. I think there would be
some advantage to not having the antennas in the same plane.

Tam/WB2TT