But in order to fix them in that position one of the clamps (I chose the biggest) needs to be “tweaked”. The closer you want to bring them together (the narrower the gap) the more you need to remove. My experience showed that I removed a bit too much, but you need to test yourself. Tools needed: a file is enough, but you may want to use cutting pliers to cut off remove small pieces of PVC first.
This is the most difficult operation.