After reading the description of your workout, I don't believe you should be exerting that much pressure on your stroke. Pressure on the device is not as important as maintaining a 80% erection and using slow even strokes. 4 second motion for 20~30 reps in 3~4 sets. That's one hell of a workout. Seated or standing you can still use a 2 handed grasp on the JD. I've been at that approach for a couple months solid now (time off for 4 wisdom teeth extractions, 2 root canals, and a bridge) with great results. I've created a meatier penis from base to tip and added a 1/4 inch in length. Which reminds me,

I need to get some true measurements and update my progress thread.