My first e85 experience.

One thing I had planned on doing when running E85 was putting a simple ball valve on the end of the vent hose to shut it off when the car sat. Whether or not it was going to keep the water out, I'm not sure. But it was an idea to help keep the water content down in the tank.

Yes, the ball valve works well on the vent tube. It also keeps it from evaporating as quick out of the cell. But even with E85, you will still have the moister issue's even in the bowls, just not as bad as alky. My friend ran E85 all last year in a SB Chev with 15:1 comp. he rebuilt the engine this winter, not any issue's from the use.
I run a belt drive pump, so a shut off was required by NHRA, this too helps keep the system from the pump to the cell closed.
Another trick you can do with E85, is install a lean out valve , this will help you build heat quicker in the motor.
You will want to get a test kit, to test the octane with E85. It can and will vary.
Don't forget to open the ball valve, easy to miss. I have a list before starting:
Shut off valve on
Vent tube valve open
Air bottle on
If my car wasn't set up for alky, I would run E85.With the price of race fuel, it is a smart move. It is just now catching on.