I decided to try sewing leather on my Singer 328k. I used a leather needle, heavy-duty thread, and went slowly. It went really well! I do want to get a spare bobbin case. I think the only problems I had were all caused by the bobbin tension being a bit tight for the thicker thread.
Now I have a new problem - how do I source affordable leather? SR Harris has bins of scraps you can buy by weight. Very affordable, but hard to find just the right thing. Maybe I'll get some $$ at Christmas and splurge on a whole hide from SR Harris.