It was 565, I changed it to 1024 and thought I saw a momentary increase (14m?) but then it settled back to similar values... I then set it to 2048 (good value?) and now I'm noticing a cyclic pattern from 7mb-14mb/s every 1-2min which I guess is an improvement since it was staying around 7 before (possibly 7-10) although the completion estimate is more varied. Thanks for the advice!
Is it safe to lower that value from 4096, could it cause corruption?
P.S I've been using the raid-disks option after reading the much earlier post. I only just recently got confident enough to play around with the 25Gx8 partition at the end of my 2T drives. I was able to add drives, Raid 5->6, Raid 6->5, Raid 5->6! Very cool!