Nav
Absolutely no way, if you do it the way you are suggesting you are asking for trouble, you want to sit the Instrument Rating Skill Test having 5hrs in the twin? you are a braver man than me I can assure you.
The other aspect is that if you are planning on going to the airlines do you really think they will view your IR as a multi IR? and I think in the world of JAA land this would not constitute a Multi IR course anyway (someone can clarify better than me here), a multi IR is just that, the whole course is done on a multi, same with the single IR.
Dean