I used an MK quad frame I built up from leftover bits and a few odds and ends I had to buy to make it a complete frame, worked very well and as most F/C's have hole spacing that matches the MK F/C it was pretty easy to swap boards on and off the frame. It was the original test bed I used for my first WKM and after I got the second one it kind of became the permanent home for it and the cast off Coptersky GoPro mount I had on the shelf, it is now my Naza controlled APV quad that has been in a lot of the videos I've done with both WKM and Naza on it.
The other option is to get one of Rusty's Mini Quad frames, really inexpensive and pretty robust, both of my aerobatic KK qudas are built on this frame and I can attest to how much abuse they can take, including getting dunked in a stream...
http://www.shop.aglhobbiesllc.com/Rusty-s-MQ-1-Frame-Kit/MQ-1-Frame-Kit.html my new testbed frame is going to be another one of these.
Ken