bubs...sorry it's taken a few days to reply to your PM. To answer your questions.

I also built a subfloor ontop my cement floor. I bought 14ft 2x4's and layed them across my 14'3" wide room with 16" centers.
You can see the setup in these photos:
http://forum.ottawagolf.com/showthre...l=1#post479593

I nailed the 2x4's into the cement floor with a ramset. You can see I built a housing around my hitting & putting sensors. Have the sensor housing in place then nail the rest of the flooring around that housing. I then screwed 3/4" plywood on top followed by a nice dense padding (yellow). The putting turf covers my entire floor...I had bought that years ago directly from AboutGolf when I was hoping to have one of their units (I never won the lottery).
I have a friend in the carpet business cut the slots for the putting sensor out for me. Here was his trick. We put 2 strips of tape over the putting sensors and colored the indentation with a black marker. Rolled the carpet back onto the putting sensor and pressed down on the putting sensor. When we rolled the carpet back it it left 2 perfect black strips on the underside of the putting turf. This gave him the exact location to cut out the strips for the putting sensor. Sliced out the 2 strips...layed the carpet back down and it was perfect. Let me know if I can elaborate or help in any other way.