sleeves are growing

I have begun the right sleeve on my Sahara. I have only ever knitted jumpers in pieces before, so I'd make the sleeve and then attach it to the rest of the jumper at the end. This one however is kinda just growing out the side of it and it's very different. The pattern is for 16" sleeves, but I think I will have to have longer sleeves, cause my arms aren't that short.

I swatched up the red wool I have, and it seems like it will work well for my red vest. It's a very very bright red, I will have to post pictures once I cast on.