Helmet setup inquiry

I am setting up my helmet and have some noob questions.

I do not want/need to spend the money for my own NVG setup. I am in the reserves and my unit uses PVS13s and 14s. I recently acquired a fast helmet that came with a shroud. On my old helmet I have a Rhino mount.

Is the mounting the same between a rhino and shroud? I am looking for just the mount since I want to use the J-arm that comes with the NVG as a way to save cost. I have seen and do not really want to spend the money if I do not need to on Wilcox G11, but is there something similar?

For the counterweight what is it that people use? I have thought about doing a battery pack but curious on the actual weight and how it has been achieved.