I don't buy a bigger size. But then I don't use batting which will make the garment much bulkier. I use the same size that I would use if I was making it out of a regular fabric. When you piece onto a base fabric with quilting cottons, you basically end up with a heavier weight fabric that would be comparable to a sturdy twill or light corduroy so no need to size up for it to fit.
Angelmama, this pattern is a very old Simplicity. I have a couple patterns with straight sides and a good shoulder line for me that I just reuse with adjustments like longer length, cuffs, pockets or whatever. One of the patterns I commonly use started life as a big shirt pattern. I liked the shoulder line as it fit me well and I liked how the sleeves fit so I just widened the sleeve, took the collar off and lowered the neckline and made a straight bottom. Instant jacket!