ha ha
errrr, well i dont know, i followed this video... https://www.youtube.com/watch?v=Cp6ijKqhDN0
and used the ones spec'd and it worked on a single HD.
With the bit before, im not sure which pat file got uploaded, i think it was DSM_DS3615xs_23824.pat and ive pasted the wrong one in my previous post. It only would accept one of them, so i couldnt install any other.