@kbro:
what about installing on a e.g. 4GB SATA DOM? So you dont have to care about reliability of USB devices or USB controllers.
Just use one SATA slot onboard which should be available cause you're using a H/W raid controller anyway. (you just have to care about power connection, cause a SATA DOM usually needs one)

So the SATA DOM will be handled like an internal hard disk and 4GB are not too expensive and enough for dssv6 and any further updates.