Owen,
I don't think the FAA has any prohibition regarding ME after IR either, but I believe a check ride is required to exercise the privilege.
I never could understand why one would do his/her instrument training in a single then slap a few hours of multiengine time on top of that and feel comfortable smashing off into IMC in a twin. Seems like a death wish. Maybe not - I do tend to catastrophize some.
I was extremely fortunate in that, after passing the private pilot exam (Cherokee 140 - Old Faithful), I was able to hitch rides in an Aztec - scheduled freight flight from CLE to Detroit Metro and back. Every flight was IFR at night, over the lake. The pilot assigned to that trip was a good friend and ATP/CFII so I was able to log a couple hundred hours of multi/inst instruction time without cost. Well, not completely without cost - I had to buy him alot of beers after the flights.
The first time I ever flew a twin in daylight was for the ME checkride (crappy touchdown but I passed). So all of my inst. training and inst. flight test was in the Aztec. From a competency/safety standpoint, I can't imagine one wanting to do it any other way.
Try a SE go-around in a light twin IFR at night - with snow.
Guaranteed you will have your hands (and shorts) full the first few times. Good Luck.