The pressure is impossible to estimate without knowing the vessel, but you absolutely can use a spunding valve with plastic.
Holy cow- you guys did it. The Kickstarter was successfully funded! Now the real work
Monticello Barleywine, Red Nosed Tripel
Cali Common, Imperial Common, Sunshine Belgian Rye, Sticke Note Alt
Cherry Blackberry melomel
Belma Pale Ale, Cluster Fug IIPA, American IIPA v1.0, rauchbier, roggenbier