Root beer - so much foam!

[dvdapex]

I've read tons on this issue, tried several different things and still have an issue where when my force-carbed root beer is poured there's a ton of foam and little carbonation left. Here are the details of the pour:

EVA Barrier 4mm line 15 ft (I've also tried 8ft and 10 ft and it wasn't any better.).
duotight connections
Carbonated at 35 PSI for 10 days, taking the keg out to shake it to get more gas 3-4 times during the 10 days
dropped to 10 PSI, pressure released the keg immediately before serving
keg is kept at between 36 - 38 degrees
use this duotight beer gun to serve

I've tried pouring into a refrigerated glass, a glass filled with ice and a frosty mug and they all result in foam-ups with little carbonation left.

What else should I be trying and/or what should I be doing differently?

 

[dvdapex]

I turned the serving PSI down to 6. It seems silly (based on what I've heard the major benefit of the product is) that 15 ft of EVA Barrier 4mm line still needs serving PSI at 6 to keep from losing all of the foam, but there you have it...

 

[efnm]

I'm dealing with the same thing for my plain seltzer. The transition to foam releases all of the CO2 and I'm left with flat water. I'll have to give this a try.