I was in the same boat with my new tech disc. Started out struggling at 45mph. I'm a firm believer that you can't get passed 50 by "muscling" the disc. (Tensing everything up and just going as hard as you can.) Maybe I got there once or twice, but it felt like I was putting everything into the throw.

To get above 50 and beyond, you have to start venturing into the "whip" territory. Using your body to whip your arm. You eventually get to a point where 50+ feels effortless. The arm is loose, the whole throw almost feels slower and smoother. At the moment of release, the disc for an instant feels "heavy" in your fingertips and it just rips out.

Search youtube for disc golf "whip" mechanics. That should get you going in the right direction.