We don't space for larger sizes, rather we place them 4" off center, in this case on both sides. We have never had a complaint about it in 31 years here. Maybe we're just lucky, but I don't think so. The center of a shirt is in the same place on any size. But, if one feels they need to do that, as I have seen in more than a few discussions, then go for it. If I'm reading this correctly, then it's the company name on the left, and assorted years of service on the right, then I'd set it up as multi-color job, and swap out screens for each years of service level needed.
Steve