well, it wasn´t very professional, but ......ok.
At that place where I wanted to widen the shell, I used the handle of a screwdriver.
It was big and small enough to make enough place for the toe.
I prevented my hand of the tip from the screwdriver with a greater metal piece to have enough force for pressing.
But even with hardest pressing I had to overheaten the plastic a bit.
Or it wouldn´t have worked.
Btw: a normal hairdrier gives not enough heat.
I used a semi professional hot air drier.
(used par example for removing varnish from wood)