My big molds (.715 and .610) are singles, and my smaller ones (.454, .380, etc.) are all doubles. For the occasional shooting I do they are just fine. I also really enjoy casting, so I don't mind taking my time. I've never used any of the large "gang" molds, but I've seen issues like those Grenadier mentioned come up in a few videos I've watched. I think I'd be inclined to get more experience with casting before jumping into a high production mold, if you decide you really want one. My singles and doubles will suit me for the rest of my life. 
