Hardware Insert question

[mcbv]

I wired my old spx 90 up to my 002 Rack. Output #5, inputs #'s 5&6 on the 002R (mono in, stereo outs on the spx). My problem is that I can only use the spx as an insert on one track only, by selecting i/o 5&6 from the insert menu. If I try and select it on more than one track it says that 5&6 are already being used by another.
So, how can I use the spx as an insert on all or any of my other tracks? Is there a different hard wiring configuration, or preference set up or something else I am overlooking?

Thanks in advance for any help.