You are doing great! It's important so you want to do it right, that's why I first came to this site and why I stay to encourage and learn more myself.
That is also the spacing I would use if you are using indeterminate tomatoes. Determinate and bush type tomatoes are smaller and you know before hand how tall/wide they will be growing. I would still prune the heck out of them for better management, less chance of disease and bugs and so you can actually find the maters
There are lots of videos on youtube if this is new to you. If you have indeterminate maters, you might think about using a cable above them and using the yo-yo type tomato hangers to give them stability in the system. These are similuar to the commercial ones and have really good reviews. Somewhere on this site is some pictures of this type of system.
Unless you purchased the "heavy duty" type net pots with the extra large lip you will want to make the hole slightly smaller then the top of the net pot. Remember since the hole will be on a "curve" due to the round pipe they tend to sway with the wind but it dosen't hurt the plants and I have only had one fall out from very high wind. Tip: I saved the cut outs to help level the pipes since turned upside down they fit the pipe perfectly and a few of them on one end give the pipe that "just off bubble" angle.
Lets see it already....