A R2 ROM will work in a R1 machine. It is the vice versa that is the problem. That is why you can put a R2 cpu board in a R1 WS, but not vice versa.

It working in a R1 means:

It works

It works in a R1 b:

It may work in a R2 :-/

So, at this point...

Feeling lucky... punk?

Unless of course I'm wrong and you can't use R2 cpus in a R1, but I'm pretty sure you can.