Yes, I'm not saying DM didn't have the satchel, or obviously the gun, just that it's not something you see carried every day in this neck of the woods, and I believe either SB or the tenant would have noticed it. In any event, it's MS' account of suddenly pulling over in the dark and actually seeing DM put a gun in the satchel that I am suspicious of. If he testified that he saw DM put something in the bag and then concluded a little later that it must have been the gun, I would be more inclined to believe him.
I'm sorry, but I am highly suspicious of his self-serving taking the stand; exonerating himself from all prior knowledge; assisting only out of shock and confusion. As someone else said, he could so easily have driven the Yukon straight to the police station that night. His rush to obtain DM's drugs, even if Miss MM wanted to smoke it all, doesn't jive with his declared horror, any more than wanting to attend his sister's wedding, and the associated partying. To me there is sufficient evidence, forensic and circumstantial, to convict him of 1st.