Options for two Hero3 non plus

Cleanest solution is to use the GoPro stereo rig and cable. It's designed specifically for that and the cable is made by GoPro so you know it syncs properly. I had thought they had an earlier 3D rig that was compatible with Hero 2/3?
And there have been rumors of GoPro4 update but doesn't sound like that's happening.

Second choice would be custom cable with their rig unless yo want to configure something different and have the ability to build a nice rig.

Dual Hero System works great with Gopro 3+ Black. It is only compatible with Gopro 3+ Black.
http://shop.gopro.com/APAC/accessories/ ... D-301.html

You can tweak (aka cut the plastic housing and reroute the cable) of the DHS to get interaxials to 90mm. There was a DHS for Gopro 2 but that did not work for any Gopro 3s. I very much doubt if there will be a DHS firmware fix for Hero 4s now (with its successors just around the corner). Gopro say their upcoming Hero 5 (or whatever it will be called) will have synced capability for the 6 camera array for 2D 360 videos it has announced. Whether that means there will be a DHS for Gopro 5 generally is unannounced. Also their "Project Odyssey" 16 camera rig for 360 3d videos with Google's Jump platform will have synced Gopros.
https://www.reddit.com/r/oculus/comment ... ray_has_a/
You might think 3d sync for these camera arrays would mean 3d generally for Gopro 5 Black but it aint necessarily so .. going on previous Gopro griefs with 3d (major firmware bugs with Gopro 2 3d, non-delivery of DHS for Gopro 3, non delivery of promised firmware for DHS use with Gopro 4)

Their 6 camera array for 360 2D videos should be hackable for pretty good 360 3d videos if the cameras are modded with super fisheyes like Entapano lenses.

Gopro share talk is positive about their vr and drone developments so I think we can be sure 3d will be an ongoing part of Gopro development eventually
http://www.thestreet.com/story/13239721 ... ntial.html