I can sympathize, Robert. As one of those "thumb-over" type players, my thumb was hurting after playing hours on the significantly thicker neck of my new 12-string, trying to hold down both strings of the lowest course on what would otherwise be a barre chord. However, continued practice and just playing through the ouch seems to have relieved that issue, thankfully. Maybe that will happen for you?
Current acoustic guitars: --Eastman E10D, 2018 (solid Adi spruce top, solid mahogany back and sides) --Eastman E8D, 2019 (solid Sitka spruce top, solid Rosewood back and sides) --Guild GAD F212 12-string, 2011 (solid Sitka spruce top, solid mahogany b&s) --Guild OM-140ce, 2018 (solid Sitka spruce top, solid mahogany back and sides