Very nice install.
I can't justify 2 tablets for very occasional use.
I did a 'custom' install.. well more of a lash up last year by using only one android 10" tablet. I got a generic tablet holder from cpc.co.uk, then built an extension arm onto it. This extenstion arm was tie wrapped onto the headrest posts and so positioned so that the tablet was right in the middle of the two front seat. Then attached a headphone splitter cable, and voila a rear seat entertainment system, so you can watch the same film OR use Freenav to follow where you are going.
Lash gear up is now in the garage but will be out in the X3 for the January France ski trip drive.