This is the antenna holder I've been wanting to make for years, a universal one that can hold almost any T antenna on almost any quadcopter's standoffs, capable of handling 19mm to 31mm standoff distance and even wider/thinner, the purple standoffs shown here are 30mm apart (center-to-center), the black ones 20mm distance.

It was finally made possible by using my recent print design, a very strong TPU cable tie which is used at 80% scale in this antenna holder design, see just how strong the cable tie is when printed at 100% and 150% scale in the 7th & 8th photos here: https://www.thingiverse.com/thing:5523089

I've created 3 variants to go on 5mm & 6mm diameter standoffs: Horizontal, Vertical, & Dropdown where it's held sticking out and down below the back of the craft.

Print in TPU, 0.2mm layer height, no support, 3 perimeters minimum or 5 perimeters minimum for completely solid arms. Takes just 30-40 minutes.

My prints of them weigh 1.9g to 2.5g, and the core holder without attachment arms just 1g.

Here are direct downloads of the mounts from my website.

For 5mm standoffs:

http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_5mm_Standoff_Mount-Horizontal.stl
http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_5mm_Standoff_Mount-Vertical.stl
http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_5mm_Standoff_Mount-Dropdown.stl

For 6mm standoffs:

http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_6mm_Standoff_Mount-Horizontal.stl
http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_6mm_Standoff_Mount-Vertical.stl
http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_6mm_Standoff_Mount-Dropdown.stl

And the core holder for you to remix and add your own mounts:

http://www.haku.co.uk/3D/Rids_Universal_T_Antenna_Standoff_Mount-Core.stl

After printing, give the cable ties a stretch first and pull the hoops over the pins without an antenna in to see first hand how it works, you might find it's easier using pliers to hold & pull the tabs on first installation of the antenna.
TPU will settle a small amount into whatever shape it's stretched/squashed/bent, making future use of those cable ties easier, yet they'll still hold strong.

Use knurled standoff posts, the TPU grips them so much better than smooth ones.

If you love this design, a couple of bucks would be nice https://www.paypal.com/paypalme/Haku3D Cheers!
All donations encourage me to make more designs for everyone to benefit.

Oh and who's Rid? Me, Ridwan Hughes, but most FPV people may know me as licensetodrive on YouTube https://www.youtube.com/user/licensetodrive