I've never heard of anyone complaining about the weight of a ramrod. It's really nothing. And yes, carry it under the barrels where it belongs. On many old guns the hammers are a bit heavy and hard to cock, especially both at once. I hunt behind pointing dogs so getting them both cocked isn't usually a problem. The normal carry is capped at half cock. Many times you aren't going to get a quick second shot off - it's one of the problems hunting with a SxS muzzleloader.
What you carry makes a difference. A capper, maybe from Ted Cash, a powder horn and shot bag, maybe from Track of the Wolf or Dixie Gun works. A leather shot or powder bag with a adjustable spout for powder and shot are available and nice to use, but aren't cheap. Then you'll need wads and a way to carry them - usually a possibles bag. You'll need over powder cards [ .125 thick ], cushion wads, 1/2" thick, and then over shot cards about .028 thick. Stick to the thin OS cards so the card won't ruin your pattern. When reloading you can put a cushion wad in your mouth so as to wet it. That will clean the bore when going down. After seating the OP card, throw the ramrod down the bore a couple of time till it bounces back out. This makes sure the wad is down tight on the powder. Many times the OP card will want to come back up when you first push it down because of all the trapped air you're trying to compress. Try and have a big, almost bore size end on one end of your ramrod. With a small end, the wads will want to go sideways on you. If you're not ready at this time to invest in a nice powder or shot bag you could always buy some of those plastic containers meant for premeasured loads and carry them in a shoulder bag. Most BP shotguns loads are equal amounts by volume, of shot and powder. A 1 1/8oz load of shot would be about 82grs of 2F. You could also presoak the cushion wads in water with some dish soap and put them in a plastic baggy. There are many ways of doing it. You'll just have to find what works for you. Take your gun out to a range and see what it takes to shoot and reload a MLing shotgun. And, if you want to be real, real safe, you'll uncap the unfired barrel before you reload the one you shot. You might not want to be looking down a loaded barrel - the other one.
I almost forgot. When loading with wooden ramrods, you'll want to keep one hand fairly close to the muzzle so the ramrod doesn't flex too much when trying to push a wad or load down. It's hard to explain - two hands are used, one about a foot up, and the other near the top. Good luck, have fun, and let us know how it went.
