Hello,
Why not give ADOLUX ADX 2 a try? It’s from our host. It consists of two parts that are mixed together just before developing. It has a shelf life of at least a year, probably longer. Spur SD 2525 works in a similar way.
Kodak HC-110 has an indefinite shelf life. The fine grain isn’t as good as with Xtol, but that shouldn’t be a problem with 6x7:
http://www.stefanheymann.de/foto/entwickler/hc-110.htm
Best regards,
Wolfgang