I mentioned earlier, that the glueing from parts of the front canopy was at 2 spots not entirely perfect. I couldn't leave it that way, since it was exactly at a bend, were the pressure of the bending PMMA is high.
I drilled 5 holes (3.7mm) with a special drill into the PMMA and countersinked them (previously tested it on a excess piece), then I squeezed MS polymere glue through the holes and added nice little galvanised head screws (3x16) after previously clamping it gently down.
I do feel better now and it will not be visible after adding the paint on the outside of the canopy frame parts.
