I found this book to be extra helpful https://www.amazon.com/gp/product/B01ISFAU1W/ref=oh_aui_d_de...
Written by sleep expert Nick Littlehales who consults to major sports teams/athletes where they just have to get it right all the time. They even made custom beds to take with them when being away. Anyway, he talks about the 90 minute sleep cycles you mention amongst many other things.
