What I don't know is how to properly switch to sans serif math
"globally"/by default. The command \mathss gives upright instead of
italic letters.

If you figure that out, please let me know.  That would be great.  I am about to create an online mathematics course where I will be using quite a few onscreen presentations, and I really should be using sans serif fonts for this.  So, any help you could provide would be outstanding.

Thanks again Mojca,

Troy