Thanks you for your help !
Westhemann : I´ll try to find thin screws but the originals only have 2.5 mm diameter, I think that would be difficult. What do you think if I use the original screws for metal and put a small piece of metal with thread in the guitar body ? Could work fine ?
Hector : I´ve made my first draw of the pickup template, this weekend I´ll make it with MDF. You´re right it´s fun
Biliousfrog : thank you for the link about the spring tubing, the material is PVC or rubber ?