Just thought I would drop these on. Stretching spru was the clue for me to try and do custom knobs on a panel. I tried everything, gluing on PVC, punched dots. Then got this idea.
Drilled holes, stretched spru and pulled it thru from the backside. As long as the hole is the proper size of the knob, the stretched spru will only go thru to That size! So all the knob diameters will be the same, no matter how thin the spru is stretched. If it pulls thru, just stretch another piece.
Then just add a drop of glue from the back, so as not to muddle up the front. When dry I timmed off the back flush, then the front a little longer than the knob would be. Then carefully filed them down to the finished length. Easy peasy!
If you have PVC the size you need, then just drill the hole accordingly. But the method above, you can make toggle switches!!!! Just touch the end of the trimmed spru with a hot knife!