See this 1975 article by one of Winegard's engineers back in the day:
http://www.kyes.com/antenna/stackluge.html
If you can receive that channel when not using the Jointenna, you'd likely do best to invest in a better signal combiner instead of stacking antennas to try an make up for an inefficient combiner.
You do realize you're right on the on the back side of a 2000' chunk of rock, don't you? Very, very little signal will actually make it down to your elevation and what does will be seriously compromised.