What size jiberish do you wear as riding sized, and how large is it one you? Sorry for the ignorance, I'm just unfamiliar with the sizing. +k for helpful comments, -K for hate
I had a 4xl 2nd gen Ignant, which I thought fit great. I have some 2xl older stuff '(modern 3xl) and I don't feel like its quite big enough for my personal taste. Also now that they don't do the longer back, I would go bigger. You can always run a string through the ribbing to make it tighter