there are pata/ide ssds…i just put an ide ssd in my g4 powerbook, but there’s plenty of room in the atv1 for an inline/single plane sata/ide adapter 2.5
http://www.ebay.com/itm/Mini-7-15-Pin-Female-SATA-HDD-SSD-TO-2-5-Male-IDE-Adapter-Converter-For-laptop-/110999547832
or 1.8
http://www.ebay.com/itm/like/252083467077?ul_noapp=true&chn=ps&lpid=82
(i just ordered 1;-)
and since u r opening ur atv, u can simply install the sd version directly to it if u mount it on ur desk/laptop w/ a usb<->sata cable ($10 @ walmart;-)
so the useful answer to ur original ? (if u mean by stable, simply working) hhd install: right now;-)