UPDATE May 2016 I have added a tray for the fantastic Andoer camera. 4K for 40 quid, what's not to like? Although it is similar in size to the gopro, it is much lighter so had to make a new tray for it to balance properly. Uploaded a photo of it too.

UPDATE April 2016 . Fixed the camera clip for the gopro tray, it was arse about face.

UPDATE February 2016: I have added a specific tray for the gopro 3 Black. It should be Okay for gopro 4 as well. It replaces the generic tilt pate. All that is needed is to tap the holes in the brace to 3mm and use 3mm screws to fix the camera in place.

An assembly video of sorts is on YouTube https://youtu.be/vmH4GunDxbE
I have the 123D original design files if you want to make changes, just pm me.
I have tried to make this as flexible as possible so that it can be configured for a variety of cameras. Also the use of hollow shaft motors makes a neat installation and allows 360 degree rotation on all axes.
Your printer needs to be reasonably well calibrated because some of the tolerances are quite fine but not overly so.
When tuning your gimbal make sure you do not overdrive it so that it starts shaking and vibrating. If you do this the motors might get too hot and start softening the plastic.
Before you start printing decide which parts you need for your camera and whether you want 2 or three axis.
You will need, in addition to the 3d Printed parts 2 or 3 hollow shaft motors:
RCTimer BGM2804 100T Brushless Gimbal Motor Hollow Shaft SKU172474 (available from Banggood.com or goodluckbuy.com or ebay.
You will also need a BGC (gimbal controller) I used a Storm32 BGC but an Alexmos would also be fine.
It is recommended that you replace all the thick wires with 30AWG silicon wire so that they go through the hollow shafts easily. 30AWG silicon wire can be found on eBay.