I'd use Silisleeves when pumping. Mitysleeve works much better on round
cylinder, such as the
Mityvac and Provac. Some have had success with gaiter type pumps such as
Hydromax and Penomet. Oh, and you were quoting me! Yeah, I just used the Mitysleeve around the Penomet
cylinder without the gaiter.

I've used the Penomet in that fashion for a longer time when I've used it. But for the time being my efforts towards PE have been on the down low.
Best thing you can do with the Penomet is to get Vacu-vin and mod it. Much more power. You can use
cockrings / or -sleeves to keep your testicles from entering the
cylinder.