This pattern can be made in 4ply and dk. One of the testers used chunky yarn. So don’t get to worried about the weight of yarn you have. The gauge is mostly for an idea of what yarn amount you will need. As the pattern calls for over sized being off gauge isn’t to much of a problem.
You can change the length and the size of the pattern it tells you have to do this.
I used a 4plyso mine is light. And I made the bigger size its modeled on me at a size 48 inch chest. So you can see how much room there is available. I plan to pull this back and make it in a size to fit me. But time will tell.