MIPs is designed to allow some slip between the helmet and the retention, so if that's the looseness that you're describing, yeah, might be normal.
As far as fit, head circumference is only a part of the story - shape is very important. Specialized helmets fit me very well, so much so that I haven't had a non-Specialized helmet in 10+ years, but if you have a differently shaped head, you might want to try on models from other brands.