Possible to make custom archive template?

Thanks for all your hard work on this fantastic plugin!

Do you know if it’s possible to make my own archive template? I’m making a custom theme and I’d like to do that. I’ve tried creating an archive-testimonial.php and archive-testimonials.php but neither seems to be used when I view mysite.com/testimonials/.

Thank you!

http://wordpress.org/extend/plugins/testimonials-widget/