No, unlike what some self-flattering fat guys like to say, Castelli is pretty true to size - just when it fits, it fits better than most.....
So tempting to make some similar ignorant disparaging comment but I'll resist that urge. Maybe you could try it.
I have quite a bit of Castelli kit. Cycling bibs and tri shorts/tops.
They most certainly ARE sized significantly differently from most/all other brands.
I wear XL or in one case even XXL in Castelli, while I wear M or L in Assos, Pearl Izumi, Sugoi, Champion Systems, Orca, etc.
So tell me, if I'm assessing Castelli's sizing relative to other brands, how does my size or self perception come into it?