I needed an ARCA plate and a mount for my cheap tripod to quick swap cameras and camcorders. This one requires a minimal amount of hardware and it's still pretty sturdy. I optimized the parts for strength and printability.

I personally used PETG but I suppose ABS or PLA could work, you just need a lot of walls (8+) and high infill (40%+)

Hardware:
ARCA mount
- 5x25mm spring - cut in half, you can also use two 5x13mm springs or something like that 
- M5 Nut - x1
- M5x50mm bolt - x1
- M3x16mm bolt - x2 (for the adapter plate)
- M3 Nut - 2x (for the adapter plate)
- ¼ - 20 Nut (for the adapter plate - for mounting it on a photographic screw)
ARCA plate
- ¼ - 20 photographic screw (for mounting your camera)

I haven't yet properly tested this, but I personally wouldn't trust this plate enough to shake the tripod with your equipment installed on it using this mount.

It for sure is sturdy enough to keep your equipment stabilized on the tripod though - but do your own tests before trusting your equipment with it - I am not responsible for any damage due to poorly printed parts, improperly mounted equipment or any other type of failure.

The ARCA plate has an orientating nub that fits my Sony CCD-TRV65E camcorder and keeps it from rotating. I am not sure if other devices will be able to use this nub so I also provide a version without it. 
The plate also has grooves for gluing in TPU filament strands to create more friction between the plate and your equipment. You don't need to use them but I personally do.

Proper part orientation:  

If you don't print these parts in this orientation then your parts will fail. 

Exploded view: