A colleague of mine asked me to build a quad copter for him for where he can do photography with his GoPro, so I drew up some prices and with the 3DR quad frame and a GoPro Gimbal it was over $300 excluding motors and esc's so I went on ebay and found the frame above (Quad Frame on Ebay).
First I was concerned about those fiber glass motor mounts so I ordered replacement parts from small cnc parts to replace these motor mounts (Small Parts CNC on Ebay)
I had to drill one hole per arm to fit these but once these were on it was very firm no vibrations was going to get the better of these arms. I baught the 850kv motors and the 20amp esc from 3DR and those extended wires worked very well and neat going thru the quad arms.
I also baught the 3DR PDB and to my surpise it is quite a snug fit between the two main plates (one has to drill new holes to mount it though)
There is only two bad things from this frame
1. No parts available
2. Between the legs, battery mount and gimbal there is no neat way with the 3DR sonar mount to mount the sonar.
What nice is about the gimbal is that there are 3 servos 1 big one and 2 small once and on of the small ones is mounted in such a way that it can push the camera button, its got a nice arm and everything for this.
But I must warn you this is a bit of a lego/puzzel to build this quad you have to think a bit.
I then loaded the standard 3DR parmas for a base to start tuning the PID's (3DR Quad Parms) an to my surprise this quad ended up more stable than my own 3DR quad frame without any PID tuning, see video below.
Hope this was helpfull in selecting a cheap frame