In our 2015 and 2016 charity Texas Holdem tournaments we used "hole card" cameras but were limited to 4 cameras. This was due to the USB capture device used and the number of web cams it could use. While they work fine they took time to setup, where slightly in the way, and were seen by other hole card cameras.
Once it was decided to build a 9 camera table there was one simple rule. We must NOT modify the original table. The table is the official charity foundation table with a rather expensive cloth. Again - we can NOT touch the table in any way.