Thanks for all the replies. The power down idea was mostly for the blade. When I've used it with the 9N it will sometimes ride over where I want it to dig in. I currently have 75 pounds hanging from the blade, but figured some hydraulic preasure would let me be able to hold the blade firmly to the ground without adding weight. It's not a major issue, so power down really isn't needed. Saves me some bucks and gets the hitch working a lot sooner if I go for gravity down. Although, being able to lift the back end off the ground is mighty tempting.
I was thinking a plug might cause problems. I'll be sure to vent the upper side.
To the fella down near Rolla, I'm just a bit south of Eldon and a piece north of Lake Ozark.