If one SS works, two will work better. Check out this configuration:
I've done quite a bit of playing around with SS's in various stacking configurations, using up to four of the little devils! What I found is that you can get a significant signal boost with two in a modified vertical stack, where the "upper" SS is offset by the length of the antenna to the front, and above, in respect to the "lower" unit (hard to describe, see the picture...). I also found this combination works best when the elevation "angle", with respect to the horizon, is a little bit greater than about 45 degrees. You'll notice from the picture that this high "angle-of-attack" causes the center point of the two SS's to "line up" in the vertical direction.
In recent tests using my Zenith HDV-420, a single SS produced the following "numbers":
Dropouts start appearing at the line between "Bad" and "Normal". This equates roughly to about 37 on a Hughes E-86. The tests were done with the antennas out on my deck.
Here's the readouts when I went to the dual unit configuration pictured above:
As you can see, it made quite a difference. I recently helped my neighbor install two SS, in a similar configuration, under a 2nd-story eave and it works great. Initially, we used the 1171 amp but the cable run up the wall, through the attic, out a vent and over to the antennas ended up being 100 feet (actually the run itself is less but we were too lazy to cut the 100' cable and put on a new connector so the "rest" is coiled up in the attic...) and he was getting some dropouts so we recently switched out the 1171 and used a CM 7775 in its place so the amp portion could be closer to the antennas. That totally eliminated his dropout problem. In previous testing, I've used as much as 50 feet between the 1171 and the antennas and didn't see any difference in performance in comparison with the 7775. A 100 feet is obviously too much, however.
Here's a couple more pictures, from my earlier testing, where I tried two SS in a horizontal "stack" and then four in a quad arrangement:
I don't have all the data formatted like the others but here's a summary: With a single SS and no amp I could get a "locked" signal (dropout-free reception for at least 5 minutes...) on only 3 of the 10 LA stations broadcasting that day. Adding the 1171 added one for a total of 4 stations.
Two SS in a horizontal configuration, and no amp: 5 stations. Adding the amp: 7 out of 10.
Two SS in the "offset" vertical orientation, with no amp: 7 stations. With the amp: 9 of 10.
Quad stack, no amp: 9 stations (!). With the amp: all 10, solidly.
As can be seen, most of the improvement comes from the modified vertical "pairing". I haven't tried the "quad" configuration with my HDV-420 but that's mainly because two of the four that I used are now mounted under my neighbor's eave. Actually, I've noticed that the HDV-420 has a much better receiver, in comparison the the 2nd gen units like the E86 or the MyHD card I have in a PC, so I haven't needed the "extra" performance.
If you're interested, PM me and I tell you what PVC "tinker toys" you need.
Finally, as you are discovering, location changes (up , down, left and/or right...) con make a bigger difference that everything else combined. You need to find the best "sweet spot" you can and then optimize for the best reception.