Hey Nick, sorry your skins were tough. I've heard (and tried it a couple of times) that a couple tablespoons vinegar in your soaking water will keep your casings from being tough. I've never noticed mine being particularly tough in the first place, but I'm still on my first hank of hog casings, though I've noticed some texture differences within the same bunch - some are 'bitier' than others. For snack sticks I've had great success with the 19mm pre-smoked (or smoke ready or whatever) colligen casings. Easy to stuff, consistent texture, no pre soaking, etc, pretty legit all the way round.
Nice looking Kabanosy, got to make me some before the holidays fully kick in!