Looking for some advice on a TNF Basecamp Voyager

Today, I received my Basecamp Voyager, and I'm lukewarm about it. I like the size and I like the aesthetics. However, the main strap is barely long enough to go around my body and makes the bag ride chest high if the main portion is on the front of my body. I would like it to ride a little lower. Can I make an extension to make the main strap longer so it fits better thanks.