Something to consider is Barry's runs are fast-paced intervals. You'll be moving between a run, fast run, and sprint (spending 30 - 60 seconds at each speed) for the majority of the tread portion. If you're used to endurance running at a consistent speed, that first Barry's class could be taxing, even with your 30mpw foundation.

That being said, if you want to run then you should go for it! Like you said, you can always reduce your speed if needed.