nick14
then a CRI who holds an MEP/IR can presumably teach EFIS on a twin with a CRI/SE.
Nope, I don't believe so! He's not qualified to exercise any instructional privileges on the ME aeroplane therefore he can't. However ...
FCL.900 Instructor certificates
(a) General. A person shall only carry out:
(1) flight instruction in aircraft when he/she holds:
(i) a pilot licence issued or accepted in accordance with this Regulation;
(ii) an instructor certificate appropriate to the instruction given, issued in
accordance with this Subpart;
In FCL.900(a)(1)(ii) above, you may choose to interpret the phrase "instructor certificate appropriate to the instruction given" as meaning that teaching the operation of an EFIS system on a single engine aeroplane is appropriate to teaching how to operate it in an ME aeroplane. Even I think that a bit of a stretch but I'm sure a good lawyer could get you off if you were hauled up for it.
Again, all this ilustrates that the rules do not cover every possible situation, I'll repeat what I already said ...
Don't look to the rules for a precise answer to every situation. Take them as limitations, don't read into them things which are not there but apply your knowledge, experience and intelligence to make good decisions.
3 Point