Nashville Number Question

I have "used" the NN method to chart songs but I have a question about notating a change and wonder if anyone can shed some light.

Suppose the Chords are D  A  Bbdim  Bm G

so in NN it would be I ,       V ,   then how do you notate the Bbdim???     VImin ,IV    

thank you Beagle. I did Google it a bit and couldn't come up with an answer, but I did see where minor  and diminished as a triangle.chords are notated in lower case, so could you also notate  .So you DO put the b symbol before the notation to show the 1/2 step?
Would   bvi ▲ be correct?

from what I've found so far I was correct above, you don't use the lower case Roman Numeral for a diminished chord.  here's why - what I've seen is that technically lower case is not supposed to be used for NN anyway - that's a short hand that someone came up with.  the NN uses "m" behind the regular upper case Roman Numeral for the "proper" way to do it.

since you wouldn't write VImdim then if you use the "shorthand" then you wouldn't use vidim to be technically correct.

so for your notation above, you'd use bVIdim just like I thought above.