the total amount of extensions depends on what cards are installed. Max real ports is 128 any extra extensions would have to be dxdp
If you could get 8 of the digital ports to run from dxdp of near by phones then change one dhlc to a 16 slc. That would give 8 extra slt ports

“I have not failed. I've just found 10,000 ways that won't work.”