Yes, it is a good idea to include some testimonials on your VSL. However, don't go over the top with testimonials. Create video testimonials that are straightforward and genuine. Prospects only want to see proof that you've done what you're promising before. So just go over a few testimonials fairly quickly and tell people if they want to see more testimonials they can visit the testimonial page on your website. If they need more social proof, they will visit your website. If they don't, they can keep watching the rest of your VSL.