No doubt what I have now has worked for quite a while. I just happened to notice the metal slides in an article in GOB, and realized that they are far easier to replace on the sail... and got to wondering about the strength aspect.

Yes, a SS slide in an AL track IS probably a bad idea. I have no desire to change the track (or rather add a track to the mast) as what I have now mostly works fine. I suspect the broken slides are simply due to age.

I will consider having the battens done with double slides on the new sail.

I certainly don't need ball bearing slides or anything that fancy... the main goes up reasonably well and falls pretty fast when I let go the halyard. No point in complicating something that works.