I ended up taking the mutt and so far its been great. I "walk" him with my hardtail most of the time and he seems to really like running behind it. We've hit some moderately techy little trails in the area and he had no problems. Stayed close, didn't injure himself etc.I understand how it can be frustrating. I wish my dogs would listen better sometimes. They are dogs though. Not exactly soldiers. My doofus dogs listen good enough to follow me out riding and back without causing drama on the trail. But when another dog is involved, of course they don't listen nearly as well. Just like a kid. Time to show off and push buttons of the parent.
However, he is incredibly manipulative and stubborn sometimes. He now knows when a ride is about to end and he'll have to go inside so he ****s off into one of the neighbors yards and won't come out. When I call him to come, I can sometimes see him look over, consider it for a moment, and then bolt in the opposite direction. Make no mistake, they are testing you.