modifying question

Hi all,

I'm still swatching and picking out colors, but want to get your opinion. I need to make the XS size tube for the body, but I have long arms. At first I thought, duh, just make the sleeve tube longer, but I normally need the arms a bit wider also. Can I make the L or M size for the arms and the XS for the body without any major modifications? I haven't read the pattern very closely yet to determine if I need to do different math or can I just stick it together?

Can't wait to get started!! I'm off to the ONE lys in town that's open on Sundays.