I have a corny keg that won't hold pressure unless it's kept at constant pressure at around 10 - 15 psi which apparently is enough to compress the seal against the opening of the keg enough to stop CO2 from leaking out. I need to serve from this keg for an evening out of really short line (1 ft), which means that I'll be serving at something like 3 - 5 psi. That will immediately leak from the keg, since the pressure isn't high enough to hold the seal.
The keg leaks from the seal around the lid. At some point in the life of the keg (prior to getting to me) the opening became slightly malformed. I've changed the rings, the lid, and every piece of hardware on the keg. I've tried coating the crap out of the lid with keg lube.
The keg is currently filled with beer which is keg conditioning (at 20 psi :P), so I can't currently make any physical changes to the keg unless it involves the lid somehow, since I can always re-pressurize. I'd rather not move the beer out and back in again because of oxygenation.
Any ideas on how I can get this keg to hold a low amount of pressure, even for just an evening?