This app does just what I needed. However, it was too hard to find out how to change the URL for new tabs. I've spent perhaps 15-20 minutes clicking and, frankly, don't know how I finally got to the page that enabled changing the URL. (This may pertain to other Firefox add-ins, too.)

Would like to donate, but had bad experiences with PayPal and closed my PayPal account. Wish there was another way to donate.