So my Navdy suction base finally ripped after changing to a new car... it seems it really can't take the force of the long leg base which I now needed...
You need to cut away all the old rubber, and keep the central plastic part, which should fit nicely into this part.. and still use the large cover nut to hide this printed part..
ABS recommended as it will be heated up in the sun whilst on your dashboard...

I have tried hotglue to stick it down (as I can remove easily with alcohol), but a particularly sunny day was enough to loosen that, so am now trying double sided sticky tape, with the hope that it will come off in the case I need it too

Edit: not sure why Thingiverse preview not working, uploaded photo of STL ;-)