I used standard Chain Link Top Rail, which is 1.25 inch diameter. google translate: Utilicé el riel superior de eslabones de cadena estándar, que tiene un diámetro de 1,25 pulgadas.
The T style pole connectors do not require any drilling, they just clamp the pipes together. I had to re-watch the video to be sure. See 11:40 for some of the clamps being put on.