Hi Steve,
Congrats on your score of a 1.5B at a good price.
I have just returns to revs after 20+ years.
Your doing fine, more flight time will solve the problem. You may also want to practice turns. A sloppy turn looks better than sloppy straight line flight, plus you learn more.
Holding a straight line with a quad is different for us dualie guys. Need to only, move the thumbs forward and back. We instinctively pull left right (Even if just a little). Found I was adding a small dualie pull with many of my quad inputs.