[Answered]  Issues with string launchers

Hello, i've been using my string launchers for a while now but my launches still suck. Too weak, even with a grip. In the meantime, i see guys on yt launching freakin hard with no efforts at all. Do you have any advice?
Thanks for reading.
String launchers require a different motion than Winder launchers.

https://youtu.be/agC4YoALI7c