The Meyer 5M is the standard. I use it, and so do most alto players I know. Phil Woods uses it, Cannonball Adderley used one, among many others. You can't go wrong with it.

I play on a 62 alto as well (an earlier generation however) and use a Meyer as my all-purpose setup. For years I played a 5M until someone gave me a 5S . . . not easy to find, but I preferred it to the 5M. As I started doing much more tenor work, I found I needed a more open setup on alto so that I could have consistency in switching between alto and tenor on the same gig or recording session. I now use a 6M as my all-purpose setup (although I would LOVE to find a 6S). Going with a small chamber as opposed to the medium chamber will give you slightly more projection, but as I said, they aren't easy to find, primarily because of the popularity of the medium chamber. As far as tip opening is concerned, it all depends on you as to how you like the mouthpiece to take the air . . . that's a personal preference. I would recommend to go no smaller than a 5 (a 4 would be to closed for projecting for a solo), and no larger than a 7 (you would be sacrificing control for volume). That's why most Meyer owners stick to a 5 or a 6 . . . Good luck.