No, I built spunding valves. They're pressure valves that allow you to read the PSI and adjust it.
You can see it in this photo (If you click the link in my sig you can see more info of the idea of the system. It just uses different kegs)
So I can have it wide open to blow out all pressure, or I can adjust it to release all pressure up to whatever PSI I want it to maintain at...
It simply connects to a gas ball lock that connects to the in post. So there is no modification of the keg what-so-ever.
This allows benefits (read the forum about fermenting under pressure) You can also seal it 100% when you're at the proper gravity level. That will then carbonate your beer naturally. Saves you time and money on CO2 (assuming you keg)