English Nantucket Jacket - Time for the sleeves

Hi everyone. We have had beautiful warm weather here for the last two weeks for our Easter holidays. The children being home and the chance to be gardening has meant my progress has slowed and the temptation to knit summer garments has to be resisted.

Perhaps I should just sit in the garden knitting mu jacket. I was a bit worried about some of the comments regarding the length but measured another jacket and it was 12" to the armhole so the 13" should be fine for me.

Can anybody help with the sleeves. I want to make them full length, is it best to still cast on the same amount of stitches or start with fewer and increase to the elbow. My brain is not good at calculations at the moment.

I'm really enjoying the KAL. It makes the world a smaller place.