Stout Tap + Beer Gas, too much foam

I have my pressure on the beer gas set to 25 PSI, 10' of 3/16" ID tubing to the tap. After the cascading stops, I still have half a glass of head. Do I need to lower my pressure, increase my line length, or what?

Did you carbonate the keg with pure co2 before you put it on the beergas? If it is overcarb'd I think that will lead to too much foam. I put the keg on CO2 for a day or two to get it slightly overcarb'd then disconnect it and vent it a few times a day. I find that the beer at 40F will have a pretty nice carbonation level at 0psi. Then it is ready for the beergas.

I did carb with pure CO2 first, just slightly less than I usually carb my beers. I'll have to disconnect the beer gas and start venting; I hooked it up right away.

Everything else in my system seems good, though? Hose diameter and length, beer gas PSI?

With beergas the hose length and diameter really aren't a big deal, you don't want a pressure drop through the line the way you do with CO2 pushed beer. You want the pressure drop to be across the restrictor plate. The only reason for the gas is to supply that pressure and maintain carbonation, so you don't have to be as picky about the pressure, you can just set the pressure so that it comes out of the faucet at an appropriate rate.

Good to know, I had no idea. I might reduce the length, then, because it seems like I get a bit of foam from the tubing first, until the beer fresh from the keg gets to the tap.