Ping-Pong ball radomes tend to fall off their perches at the slightest touch:
Because I planned to take my collection along to HV Open’s Mad Science Fair, I finally used a Round Tuit for some adhesive action.
The general plan was to punch a ring from double-sided tape, thusly:
The OD required touching up the edge of a brass tube punch I’d made a while ago:
It worked exactly as expected:
Unfortunately, the 3D printed spider’s “spherical” socket has such a rough surface that the adhesive had too few contact points to hold the ball in place.
My fallback has become 3M outdoor-rated double-stick foam tape, so:
This leaves a small black ring visible between ball and socket. Recessing the foam tape by half its thickness should improve its ahem optics, although it’s probably not worth the effort with black PETG.
The Smell of Molten Projects in the Morning 
A dab of hot glue perhaps?
Yeah, that’d probably work, too. [grin]
The tape seems more tenacious and it’s definitely more flexy.