We almost always ran without check valves. It's a good idea to pinch the pressure line or pull it off during refueling to prevent filling the crankcase.
As long as you treat the system like a bladder you shouldn't have a problem. That is to say, keep the line pinched until the engine fires.
A check valve won't protect you from flooding the engine through the venturi if it takes a long time to get started.
If you build the tank into the plane be sure to pressure-test it well before installation.