Thanks for the all input...I welcome more.
I'm thinking that a 22' putt would be plenty long, though I didn't consider the 40 x 10 idea (almost like a lane pool). Pretty sure my wife wouldn't go for it. But it's a good idea and it makes me think that angling the green to get 30' from end to end would be great. this would give at least a 25 to 26' foot putt depending on where the cups are. I talked to the installer/president and the shape doesn't add to the cost it's just sf pure and simple. Which makes me think a kidney shape in about one third or less of the space would work well. They are more expensive than some of the other companies I checked out, but they don't nickel and dime you. We'll see when it's all done.
I do want about a 10' straight putt, as Richww2 said more to work on a pure stroke. Knowing that you can stroke a putt pure and know where it will go builds confidence. Our club green is tilted heavily and the only straight putts are uphill. Many of us pick a cup and practice 4 to 5 footers uphill before rounds just to get our strokes in line.
I also want a r/l putt and l/r putt. the trouble with this is that I don't want it to get boring right away. And with limited space this will be challenging. the nice thing is that you can chip and pitch to these greens. And their synthetic grass can handle it.
I've wanted this for a long time, I can't believe it's going to happen and I want to consider everything I can....short of building a course in my backyard.