Thanks to everyone who responded to my question on the RQDX3 controller. The
majority of responses indicated that I did not need to change jumpers, so I
went ahead and tried it. It worked fine. 

BTW, while looking for info on this beastie I came across and excellent
document full of posts about all kinds of DEC disk issues. You can find it at:
ftp://ftp.spc.edu/third-party-disks.txt.

-Blake Yeager