It would work but you might not have very much natural vacuum (unless there are a bunch more taps on this same line). It sounds like you will be using tubing for both lateral lines and mainlines. If this is the case I would use a Y instead of Tee when going after that one tree 10 feet away. I would not waste my time or money on a guide wire because you should be able to keep things real tight because you are using tubing. Try to have 25+ taps per lateral line so you will get natural vacuum though.

Spud