[Cosmoline]

I don't know why I never thought of this before! I've been running around for years up here without a good place to keep my large knives. I don't want to attract attention by putting a large sheath knife on my belt, but the fact is I have need for a large knife all the time. I was fiddling with the off hand side of my shoulder rig when it dawned on me that I could simply hang my Puukko off the rig to balance out the revolver. It's worked quite well, and sits comfortably either behind my arm or just in front of it.

[hso]

As long as you're carrying it as a tool instead of a weapon that should work well. Be sure to try it at different "heights" so that you can get to it with your off hand with a little effort if you've got you right tied up.

[HiWayMan]

Andrews Leather makes just such a rig.
http://www.andrewsleather.com/
It is an option on their Monarch Rig.

[Lo.Com.Denom]

Just remember to take it off if you need to use a rifle or shotgun, too... unless you keep it low enough, I guess.

[Cosmoline]

Recoil wise I tried it out at the range and it's not a big deal for a carbine. It does need to be pushed to the back side of my arm for a full power rifle. It allows a draw in about the same amount of time it does from the hip, but it's mostly utilitarian not for combat. Not that my UHC puukko couldn't do some damage. But I use it for cutting up game and animal parts for dogs as well as other day-to-day slicing needs. It's a superlative blade and will cut a chicken in half with one push and no sawing motion.

Look at that Andrews "Firepower" rig on the link Hiwayman posted!! It mounts a SHOTGUN on a shoulder holster! I thought I was pushing the envelope.

[pendentive]

get a "merc harness" (or make your own) and a kydex sheath and you'll be set. real easy to carry, and you could keep your holster knife-free.