I recently had to open bellows on my old Beseler 4x5 just about fullly open for the first time ever in order to do some tiny prints. The bellows came away from the upper metal frame, to which it had been originally glued.
I was planning to use some ordinary supermarket contact adhesive but was wondering if there's something better.
A contact adhesive is fine but don't use an ordinary household glue. Most OEM bellows (since WWII) use Evostick or equivatlent to glue them to the frames.