This is a simple little mounting plate I made with tinkercad to fit on the bottom of my SK450 quad to hold a gopro arm and camera.
The mounting bracket is 34mm x 28mm by 12mm heigh with a 5mm hole in the centre and the washer is 15mm diameter and 3mm thick with a 5mm hole.
The bracket has 4 fixing holes of 3mm diameter at hole centres of 24mm x 18mm which fits on the base plate of my sk450.
The bolt down the centre is M5 so the nut is 8mm across the flats.
The slot in the centre of the mounting area is also 8mm so the nut is captive ( I would use an 8mm spanner to hold the nut so it dose not try and spin and damage the quad base plate)
The mount and washer weighs 6g , see pictures for all combined weights.
The black arm is a part I had with my gopro but there are a lot of gopro parts on thingiverse already if you do not have one.
The other parts are available here..
lens strap http://www.thingiverse.com/thing:583650
gopro hero 3 light frame http://www.thingiverse.com/thing:212082
The washer is to go in the middle of the arm so it is not crushed when it is clamped against the bracket ( can bee seen in pic 3)
see instruction for materials need .
hope you like it .
P.S The battery tray in the pictures is here :) http://www.thingiverse.com/thing:602660
I printed my mounting bracket and washer in ABS at 0.25 layer height and 50% fill.
I had the arm but if you do not you will need to find one online or print one.
To fit the mount I used 4 off M3x10mm cap head screws and 4 off M3 nyloc nuts.
To hold the arm to the mount I used 1 off M5x30mm cap head bolt with washer and 1 off M5 Nyloc nut.
Remember to fit the printed washer in the centre slot of the arm if you are using the same type as me to prevent it being broken.
When the camera is not going to be used the arm can be left in place like in pic 2 but remove the little dome nut in the arm as it will fall out, I found that out when I came home from my test flight and it was missing :(
Hope that makes sense if not feel free to ask me a question.