After my flying is over for that plane, I usually disconnect the fuel line from the carb then run the engine dry. Then I drain the tank, putting the fuel right back into my fuel bottle, then I use a short length of brass tubing and connect the pressure line to the fuel feed line to form a loop. That keeps the outside air out and prevents any left over fuel tht the clunk may not have picked up from getting all over everything. There is usually an ounce or so left over in the bottom of the tank that may come out.

As far as nitro content is concerned, whatever works.. works. I usually pick up 15% nitro because that's what's generally available and runs just fine.

CGr.