Castelli are renowned for being very 'italian' with their sizes. I've found a lot of DHB kit, is more generous, size wise. and Assos is quite 'normal' as well. Rapha is Castelli-esque, I.M.E.all my castelli kit is 2xl and fits fine
46" Chest
38" waist
i have the gabba, aero 4.0I'm a similar size to you now, what jerseys do you have?

being Italian the size referred to is willy size which for me means that all Castelli stuff is too small![]()
Evans and cycle surgery usually have a decent range. Sigma in Kingston has loads of clothing but it's all high end, Rapha, Assos, Poc, also castelli.This is it really. Certain brands, often Italian, come up a bit small, and anyone with a stocky, muscular, large chest, and broad shoulders will struggle to find a good fit. As @moo said, DHB might be a good option, but check whether you're ordering the right style; 'active' will have more room than their 'performance' version.
All this wouldn't be an issue if there was such a thing as a LBS that had a range of clothing in a variety of sizes and styles that we could actually try on. But................nostalgia isn't what it used to be.