Ok. So I reached out to Alyssa. She tells me that they have cherubs in their display tank at Seahorse Savvy and they do well with the seahorses there. She didn't say anything about any particular strategies to make it work, just that they are very peaceful fish and that she has sold quite a lot as seahorse tank-mates over the past year and doesn't hear of any issues with them. Yes, she is the seller, but I honestly trust her word on this one.
Several of my students have requested that we get an angelfish since I set the tank up in my classroom at the beginning of the last school year. My response has always been that you can't really keep one with seahorses (I've done my homework on seahorses many times over). But if I'm going to go by Alyssa's experience, it seams like this one may be different. The cherub angel, or Atlantic pygmy angelfish (Centropyge argi) is the smallest and most peaceful of the angels. I think that my system set-up (90 gal. with lots of caves for both the seahorses, angels, and others to hide), and feeding practices are conducive to success in this situation, so I'm most likely going to try it before long. I'll let y'all know how it goes.