Personally, I would do a toile, especially as you haven't used the pattern before.
Use an old sheet, or a couple of old T shirts if it's a jersey type fabric.
It's awfully disheartening when you spend a long time on a project and it just isn't going to fit.
I've just done a toile for a Butterick pattern, and thought it was nice enough to wear - until I tried it on! The sleeves are too low, and it's too big!
Btw, have you looked at Pattern Review to see what other sewers thought of it?
Jessie