Step Height
As a certified Step instructor, I would like to politely point out that anything higher than an 8" step height, no matter how long your legs are, is extremely risky and injurious. Most people do not execute proper stepping technique on higher benches.
The leg that steps up onto the bench should allow for full range of motion through the hip and knee joints (think standing tall), and landing should always be a controlled toe-ball-heel movement with no bounce. When I teach, it amazes me to watch the participants who consider themselves advanced. Advanced doesn't translate to just being able to follow the choreography: proper technique coupled with the ability to follow = advanced exerciser. These participants pile on the risers, then either step up in a perpetual squat-like position, bounce off the step on their toes when they land, or both. Often their heels never hit the floor before stepping back up again.
Full range of motion through the joints will drive the instensity up a lot more safely than the number of risers. One would be much better off using full range of motion arm movements and ditching a couple of risers. Getting through to these people is really difficult - one particular woman who I tried to help failed her practical exam due to the ballistic landing.
In the earlier videos (Mega Step Blast, Step Max, Step Heat), Rhonda lands with a little bounce in her step. It is certainly not as pronounced as what I have seen in my classes and her form is much better in later videos, but it an example of what not to do upon landing. (For the record, I adore Rhonda and think she is a perfect example of a fit, healthy, intelligent woman as well as my favorite background exerciser.) Cathe and Cedie have the landing nailed.
This might be a good time to point out that many seem to be experiencing aches and pains with these new videos which may very well be due to incorrect form and body mechanics. Unless you have access to a professional who can evaluate your technique and provide feedback, it might be best to use Cathe as your role model and try to emulate her technique. Placing lighter intensity workouts between the intensity series is also a good idea.
-Roe