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.