Ian -- I am definitely going to give the glass carrier a try. Also, thank you very much for the explanation of DOF and enlarger alignment. It was an excellent explanation and very enlightening!
Kevin -- The problem I am having is that when I focus the projection at f/2.8, the grain is sharp. When I print stopped down,though, the grain is not even visible in the print. I have printed from these negatives in the past on different equipment with pleasing results, so, in this case, fortunately, the negatives are fine.
tkamiya -- I had initially ruled this possibility out simply because it's such a struggle to get the enlarger head to move at all (it could use a good greasing, I think), but I will definitely take your suggestion and check.