Alright, I fixed the stiffness problem. The issue was that I had pushed the bottom of the "V" of the sealing covering too deep in the surface gap, actually below the level of the hinges. That meant that when moving the surface in one direction, the covering over the hinges would crumple over itself hence causing the resistance. To fix the problem I cut relief points in the sealing material just over the hinges and bingo, the surfaces move a lot easier now. It is still slightly stiffer than if was before I sealed it, but that is normal and expected.

One problem solved. As for the missing adhesive on both rolls of clear Ultracote, well...