I can imagine that they wanted to avoid shooting at beam elevation below zero and with valley slopes as a background in case Israelis used valleys to sneak between Dvinas - OK, but where were Neva batteries with their short range capabilities and shorter reaction time? I had hard time trying to defend "Dvinas" in scenario 2. For example, 5/11 is at the edge of only Neva 5/14 engagement zone.
The locations of Dvina and Neva should be made in exactly opposite way! (elevated positions is another issue)
Some time ago I wrote some contribution about czechoslovak SAMs building and one thing I noticed that layout of S-75 (SA-2) and S-125 (SA-3) is not ideal but their disposition was created in such way because at first were created SA-75/S-75 batteries and only later this was supplemented in some areas with S-125 in insufficient numbers. Basically if you want to create "ideal" defense posture you need from the start to think about both SA-75/S-75 and S-125 coverages but in history most of "eastern" nations at first built only S-75 coverages later supplemented by S-125 which was not ideal but too expensive to readjust.