Wow, the ole "rock and hard place" situation. Bah Humbug, I HATE those.
Well, if good ole Dr. Schulze were answering, he'd be really blunt and say something like, "well, if you choose to use wimpy herbs, you can expect wimpy results, but that's you're choice". sigh, which IS the truth.
BUT, Dr. Schulze spent two decades in clinical practice curing people of Incurable Diseases (he said most were "the walking dead", as the majority of his patients had been treated for years by allopathic physicians and given the 'you have 2 months to live' prognosis...and when they got to his clinic door, they'd already outlived their prognosis). So one can easily see why Schulze couldn't afford to 'wimp around' in any way, shape, or form.
So, as I see it, you're probably NOT using the Master-Cleanse as a method to cure an "Incurable", rather you're using it as just a stepping stone toward better health. That leaves you with two choices...use less of the "good stuff" or use the recommended quantity of the "wimpy stuff". Since I also have issues with seriously "hot stuff", the only thing I can tell you is this...when taking the high HU Cayenne, I've been flabberghasted that "the burn" lasted less than 5 minutes! And it lasts even less when using the tincture than the powder.
If it were me, I'd go with the good stuff and use a bit less (since I now know that the burn is so short lived). I'd use it as a challenge to get myself accustomed to using Cayenne, as Cayenne is a fabulous healer and an unequaled addition to ANY herbal protocol to force the herb in question into greater circulation throughout the body.
I'm sure zillions of folks have used wimpy, low HU, Cayenne with the Master-Cleanse (or absolutely none!) and still obtained great results, so the choice is all yours. I just prefer to 'step up to the plate' whenever I'm challenged, and use the opportunity to overcome whatever I feel I need to overcome. And utilizing Cayenne for healing is definitely one that was important to me.
Do what you and your "doctor within" feel is best for you right now...but don't fail to remember that you've probably taken all KINDS of toxic medicines throughout your life that had FAR worse side effects than a bit of a burn.
Happy cleansing...you're doing a great thing no matter which you choose!