I am not a mechanic. So please take what I say as just something from an average Joe. Hopefully someone can shed some more light on the subject.
When I installed my cloth it was the dead of winter and I went with the recommended index. In a few months summertime rolled around and it relaxed to the point I felt it wasn't tight enough.
Re-stretching was more tedious than initial install. The reason being you already have the pockets cut and have to basically anchor one side and just get the cloth right by feel. I think I ended up getting about another inch stretch, but with the pocket cuts it had to just kind of be played with. The cloth has a feel to it and you just have to get that down. You can feel the stretch in the cloth and you want to feel it springy but not overstretched. Kind of like cutting with scissors and sticking your tongue out.
It ended up stretched nicely but there was stretch shadows in the cloth afterwards. On the initial stretch there were no shadows. It didn't effect play but it is a bit annoying to see.