I posted a video on the modded KU040 board:
https://www.youtube.com/watch?v=cim1-ubz4oE

It does work remarkably well, and with over-volting the hash rate could be quite amazing (compared to the low price of the board), but as it stands it requires a few further tweaks in order to be stable.  I need to add a potentiometer to the voltage control to raise the voltage AFTER the bitstream has started hashing and I also need to implement the gradual-power up feature.  Without these, the board is extremely sketchy/unstable and prone to freezing and requires reprogramming and several tries to get it to start up properly.  Not viable for large scale mining (at all), currently.

Running at 600MHz it only starts getting errors around 0.86V (default core voltage 0.95V since it is a 20nm FPGA).  With my heat sink holding the FPGA at a remarkable 40C, there is massive room for hash increases.
I believe it can run at more than 750MHz at higher voltage and maybe even 800MHz.  In the video it is running at 600MHz (x4 cores = 2.4GH/s).