Are you designing with templates that take into account different sizes? I looked into designing a jersey once and IIRC getting the black stripe across the chest and sleeve and meet each other won't work on all sizes. They won't meet exactly, and although it may look OK on a design on screen it will look worse in person. That's why most jersey designs don't let small design elements cross over the chest to sleeves across the stitching.

You might be better off tweaking the design to make the area where the trunk and sleeves connect a solid color.