knitting nerves

so i cast on the hourglass sweater in my beautiful noro cash iroha (color 22: garnet!)on friday night. i can tell you i cast on about 5 times...to do a regular cast-on, or do provisional so as to have live stitches to knit the hem with? i tried and didn't like my gauge, so i went back to a basic cast on edge that i picked up later! i was amazed at how this yarn comes to life when knitted. i finished off my first hank this evening and joined #2. i'm very excited...and nervous. the pattern gives finished measurements...and the one we'll deal with is chest circumference. the given sizes are 33, 37, etc. (because those are the 2 i'm dealing with). problem: sorry if too personal ;), my "chest circumference is 33.5...so can't do the 33, right...but the 37 seems like a lot of ease. AND i read that the cash iroha grows with blocking. oh no...what to do. i am thinking that i may not do the full increases for the chest circumference and do a bit of an in-betweeny thing? anyone have any suggestions? i cast on the full amount of stitches for the 37 size, hemmed it as i went and it looks great. the silk/cashmere/wool blend is so amazing...little lumps of cashmere here and there with the shine of the silk...oooooh. i have only done two of the decrease rows so far and have one more to go (so really, time to think before increasing!) i'd love your thoughts!!! i love knitting and hate the guess work (that could easily be a general statement across the board for me!) i want things to go exactly as they should! so...to stick to the pattern or stray??? let me know...