How to make modgen always treat parallel transistors as m-factor

I'm using Modgen to create neat matched transistor structures, but there's one thing I don't understand about it. In our design kit, the transistors have no m-factor property, so I create multiples by specifying the instance names like "MN1<0:3>". Now when I add a pair of these to the Constraint Manager and run Modgen, then click on the Pattern Editor, the transistors will be displayed in any of three different ways:

A: MN0<0:3> (4)
B: MN1<0:3> (4)

or

A: MN0<0> (1)
B: MN0<1> (1)
C: MN0<2> (1)
D: MN0<3> (1)
E: MN1<0:3> (4)

or

A: MN0<0> (1)
B: MN0<1> (1)
C: MN0<2> (1)
D: MN0<3> (1)
E: MN1<0> (1)
F: MN1<1> (1)
G: MN1<2> (1)
H: MN1<3> (1)

Obviously, I want the first option, but often (usually?) I get the second or third. The only way to get rid of this is to completely delete all constraints, delete the offending transistors, place new ones with different names, and hope that this time it works correctly. Of course I can still make my matched layout if the transistors are not recognized as belonging together, but it's just extremely annoying to figure out what I should write down instead of ABBA-BAAB.

I noticed that there is an entry in Sourcelink that says that this should just work in 6.1.3.500.3 (I'm using 6.1.3.500.13), so could I be doing something wrong here?