What's your batch size, a quarter pound of Spec B (what, ~1%?) doesn't seem like it would be that out of place...IMO. Being the only Caramel malt, with plenty of Munich base to be the main component seems you will be getting just what you are looking for, maybe leaning a bit more Dopplebock.
I would have thought maybe a lower mash temp? Never brewed a Bock myself, just might need to some day.