I also use a mod sitdrag with a battle belt and love it.I started using one with my sit drag and sold my mantis. Have not regretted it.
I have heard guys say that if your tether is too high it can make the saddle ride up.Just seeing where guys are using these on the Mantis. I am one of those who seem to always struggle with the Mantis riding up to high. Will this help? What battle belt are you using? Thanks