I am not familiar with base panel installations. Our environments are quite different. We barely see rain or frost and we get earthquakes. Perhaps that is why I don't seem them used here. They seem to have a texture to them that creates a gap underneath. I can't tell how big that gap is. I suspect, the sand will fill that gap. The bigger the gap, the more sand it will take. I just had 400+ sq-ft installed. It took a few bags but I didn't count.
Got the rest of the pavers installed and 2 layers of sand, with vibratory compactor run in between. The pavers are locking down tight and seem to be smoothing out. I'm going to work a few more bags into the cracks, then apply water to seal. BTW, the plate compactor did break 2 pavers but no biggie. I love it when a plan comes together.