Share 'Has anybody created fermentors out of 15.5 gallon kegs?'

I bought a couple of Sanke kegs and would like to convert them into large fermentors. I have several questions if anybody has experience with this. First of all, I was wondering if there is a good cap to attach a blow off tube to the existing opening of the standard keg available on the general market (or easy to make from items at the hardware store.) Second, I was going to make a stand for the…