We carry the 21SF on duty. Its a sweet pistol. 13+1 in .45 ACP is hard to beat. That said, the 21 is a beast of a pistol, but doable with the right setup. I used to carry it, but now I carry a G23 .40 with a full-size 22 magazine. For concealement I use a hybrid leather/kydex inside the waist band rig. There are many models galco, comptac, crossbreed, white hat, parker, ridgid, h and r custom, as well as countless others. they are all the same design.
For a paddle holster, hands down buy a OWB paddle rig from Jim at panther concealment in Jacksonville, Florida. The best fit and finish by far over anything I have tried. He has designed a one of a kind paddle that hugs close to the body like a pancake, making it good for cc.
I carry both holsters, OWB if I have a button up shirt, IWB with a tee.
It isn't bad. You need an extra inch in the waistline. I wear 32" pants with a 31" waist. The two clip design of the hybrid distributes the weight much better than a single clip iwb making the gun seem lighter and therefore easier to carry. I put it on an forget I'm wearing it.