Looks fine to me. Congratulations on your purchase. Personally, I would wear either pants of wool or narrow corduroy as opposed to denim, but to each his own preference. Toss on a nice tartan wool tie, sweater vest or waistcoat with this jacket. Once you've decided to enjoy it, remove the hold stitches from the sides of the back flap. The flap should rest freely over your backside. I see no need to alterations. You are fortunate to enjoy right off the rack, as it were.