I do not think the 4s would be too much of an issue, it would be the weight of the lst2. A mm may have issues with that truck. In something lighter, like a crt.5 or ls10 I am sure that it will work fine. I use the quark 65 esc on 4s in both of the afore mentioned trucks and it was fine. That quark is a competitor to the sidewinder (except for the price, almost a 3 : 1 ratio!)
I ran my sidewinder on 3s in a xxx-cr with a kontronik twist 37 today and it ran very well. It even stayed cooler than the mm, not to sure why? It may have been the fact the mm heatsink was barely attached to the fets. No issue, I removed it, carefully cleaned up the existing thermal glue and used some arctic silver to reapply the heatsink. I also added a novak cap. That will serve duty on the hyper7 buggy.
Great product Joe, the sidewinder should be a great seller for you, It handily out performs anything else on the market, and is cheaper too! Not sure how you guys do it, but keep up the good work!