I just got that pack a month or so ago, after unsuccessfully trying to use the Osprey Exos. The ACT Lite pack produced an immediate "Wow" when I loaded my gear into it and tried it on.

However, I don't think it comes in different sizes (if I'm reading the website correctly.) I know the store where I bought it didn't ask about size. Instead, it has an adjustable suspension to fit everyone in that range.

My torso size is right at 21"; for illustration, when I used a Granite Gear Vapor Trail pack, I was at the top end of the medium length, and the bottom end of the long length. I ended up choosing the long length, because the medium didn't feel right.

After we got the Deuter all dialed in, I could have made the suspension longer, probably by half an inch or an inch. (It uses a ladder-type adjustment panel to lengthen or shorten the suspension. So, my guess is it will fit you OK.

What you might want to do is buy it at at a local store, if possible. Load it with your gear (not sandbags), and see if you can get it to fit properly. If there is no local store, be sure to order it from a dealer who will let you return it for a full refund if it doesn't fit. That way, all you're out is the shipping.