Has anybody created fermentors out of 15.5 gallon kegs?

[Jake]

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 keg and put a valve straight out of the bottom to drain off the yeast bed. Does anybody have experience doing this? If so, does it work well? Any tips or pitfalls to look out for? Finally, I was concerned about the cleanability of a keg fermentor. Any encouraging words, horror stories, etc. would be appreciated. Thanks!