Are you using it in the shower? I can leave a Hydromax7 suctioned on in the shower without using my hands, and no shower strap. In fact, round 2, I’ll latter and wash my hair and self with both hands while pumping. For round 3, I’ll turn off the water halfway through and towel dry myself with both hands while pumping.
I only use the Hydromax9 in the bath. That thing is a monster, and it is appreciably heavier than the Hydromax7. I’d almost guarantee you would need the shower strap to use a Hydromax9 in the shower hands free!!!