Making a dress a bit smaller - is it worth the bother?

[MaybeDoctor]

I have bought a shirt dress on ebay that is a bit too big for me. It is good quality linen, so I am wondering whether I should alter the dress. It fits on the lower half of me and has a belt to cinch it in, but I could do with losing some volume on the waist and chest area.

The only problem is that there isn't a side seam as such, but two side seams. One is slightly in front of the sleeve, one is slightly behind it, so there is a panel under the arm running all the way down to the hem. Could I introduce a dart between those two seams? Or something else?

I know how to use a sewing machine in a basic way. Thanks.

[MaybeDoctor]

Bump

[SoupDragon]

Could you try pinning it to see if it would work?

[storynanny]

It might be an idea to wash it first as linen can shrink a lot.