I want my new third Gallery to display 5 across. And I'm comfortable with modifying the Template.
But, apparently "ALL GALLERIES MUST USE THE SAME TEMPLATE"...... at least that appears to be the rule. I don't mind hacking a file (cache?) and changing the Template number... but this doesn't seem to be that easy.
Am I really restricted to ONE GALLERY TEMPLATE without some serious hacking??
Yes, you'll need to make a new cache_builder file and inject it into the UBB's portal box listing.
Hint: Why or why doesn't someone write a bridge to COPPERMINE?
It's not
Standards Compliant (even to the xHTML specification they use in their header, let alone the modern HTML5 specification that we use) or even Mobile Capable (see attached screenshot below), so it's likely not going to happen from either of us unless hired to create a bridge, and I doubt anyone is going to pay for development of one. Plus, IIRC, it doesn't even have a member system and is designed for a single user to manage a gallery; so I'm not even sure how feasible a bridge would be.
UBB.threads is a Forum platform that just happens to have a photo gallery built in; where we're more than happy to look at making things easier to use or be standards compliant, third party scripts are out of the scope of development tasks.