I've replaced a C07 with a C08 without issue a few months ago. I actually had ERR program a C11 back to C08 so I'd have a spare of the most common version. The C13 works well in anything I've put it in, but I don't have a spare of that one.
ERR is now supplying an R4LC with firmware version C08 with their products. That appears to be plug compatible with the R2LC, at least for one instance that I tested.