Oh yeah, what to do about arms in Summer is always an issue for me as I had big arms even when I was slim. Capped sleeves are the worst as they usually hit at the thickest part of my arms, sleeveless is even better than that. I live in an area that has a very short Spring and a long hot dry Summer so I look for 3/4 length sleeves in linen, cotton, cotton/spandex or linen/cotton blends. This gives me coverage in fibers that can breathe. You can find this sleeve length in shirts and tess. If you have trouble buttoning the front up without gaps (which I often do) wear a white tank underneath and leave the top offending buttons unbuttoned. This also gives you the flexibility to take off the outer lay when you are at home. Another option to consider would be easy fittiig tunics in breathable fabrics. I have purchased several 3/4 lenght sleeve shirts, tees and tunics from Talbots (some of their Irish linen items are styled ok for basics) J. Jill and Eddie Bauer.
Jeans are difficult as well. I still am not satisified with the selection available especially as I can never find good dark washes in plus sizes. I recently purchased some slim fit jeans from Lands End of all places and they fit great. I was very surprised. I've also had good luck with the tried-and-true fit jeans from J. Jill. They aren't fashion forward but they do fit well and are good basics. I don't like overly embellished pockets or any embellishments on the legs and unfortunately many plus-size jeans are way too overly embellished for me.
I hope this is helpful. I'd love to know how you end up working with these "problem" areas.
