I've used a chest holster and shoulder holster with good results. Carrying a big .44 in a shoulder holster felt very lopsided, plus there's no guarantee that any old shoulder holster works well with a backpack. I like a chest holster better, and the only time it's ever been in the way was when climbing over a big fallen log. It didn't have any issues with the backpack straps.
I think Simply Rugged and Passport Holsters make chest rigs. I don't know the make of the one I used because it was a loaner.
