I've been running the Varia RVR315 for a few months now. Besides my Wahoo Elemnt Bolt, water bottles, and frame/handlebar/saddle bag, I won't go on a ride without the Varia. It's nice to have a little more awareness of the cars behind you. And it was one of those things I didn't feel I needed until I used it.
There's one thing that bugs me, the bulky, heavy, fiddly mount for the Varia. While it was designed to fit a variety of seatpost shapes thanks to its changable rubber spacers, it's clumsily overbuilt and the rubber bands don't do a good job keeping it positioned. I often take the whole mount off when I take bike photos.
There are options of mounting it under the saddle or clipping it onto a bag, but I didn't like those solutions either. I went off to design and 3d print my own custom Varia mount. I started by tracing the cross section of my Roadmachine seatpost which I then scanned and translated it to CAD:
Luckily i'm very handy with CAD surfacing and have designed many plastic/metal parts in the past:
It's a simple part that uses the included Garmin 1/4 turn interface (that is screwed onto the mount). A brass insert and M4 screw from Mcmaster to clamp it to the seatpost.
I also made a version that has a standard 27.2mm round cross section (right)
I gave the Varia unit a 3 degree upwards angle which you can kind of see in the side view.
As for printing: I sent it off to Shapeways. I went with "Versatile Plastic" which I have used before as a material to order a Blendr mount for my Wahoo to use on the BMC stem. It's fairly strong and holds up well under heat, with some flex to give if it gets knocked.
Total price (after Black color surcharge and service fees) comes out to about $19/pc.
It should be in next week. I'll report how it works and most importantly how much better it looks!