Yes it is possible to add courts manually. I am doing it myself as I get a crash with other mods. It is a bit tricky and I dont know if there is a better way to do it. But you need to use QPed or different application to be able to open .PAK files. Inside the .PAK files there is data and then courts where you can put in up to 250 courts. This is a pain in the ass to be honest. Because there is a lot of manual work you need to do. I have put in 50 and it took me hours
So you need to have a lot of patience and time to do it.
This is explained in HowToMod FAQ as well, presented by manutoo.
EDIT // As I am stupid and not reading everything to a 100 percent I missed that there is a possibility to extract the Pak01 folder so you get all the packed material in to a folder, I am not sure though if it is possible to edit everything from there. IF IT IS POSSIBLE, then you can just make maps with every court you want to and then just edit the Tour.INI file so you adjust every court to a specific tournament. That will save you A LOT of time. And me now