i still have to write it up but i've discovered that it's possible to obtain PCB CAD files on taobao for the RK3288. with mike's help (and around $20) i've been working for the past 4 days on an EOMA68-RK3288 board. the RK3288 apparently supports up to 4GB of RAM, which is the primary reason why i'm looking at it at the same time as the nexell S5P6818 (which is 8-core but only does up to 2GB RAM).
the RK3288 was apparently designed for chromebooks, hence the increased RAM. what's nice is that i have the assistance of an engineer who works for rockchip, thanks to an introduction. i'll be arranging to go visit their HQ in a few weeks, to say hello.
l.
--- crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68