I'm the one with the 75% IJ Jag, that Irish was referring to.
She's just a baby, but her momma, a 50% IJ Jag is not all that big. The sire is fairly big for an IJ, & he is the sire to to other IJ babies that I have. I expect my IJ's from him to be a little bit bigger than my IJ Jag, based on the parents. My youngest IJ is from small parents, so I don't expect her to get that big (on the scale of IJ size)
I have seen older IJ's that were huge for IJ's, so I'd have to say it depends on the lineage, that will play as much part as the species itself does.
I also have a Coastal baby that came from smaller parents, so she's not expected to get as big as most Coastals are known to get.
Do you have pics of the parents?