I don't think it is the particular shape that pairs with a blend or type of leaf. I think it is more the dimensions. Perhaps also the shape of the chamber, cylindrical or conical. I can't rattle off what dimensions and shape chambers do best with which kind of leaf. However, I think a wider chamber often does better with complex blends, four or more tobaccos, to let them burn simultaneously and give a more complex flavor. I find average to narrow chambers that are pretty deep best for burley like Semois, a burley variant. Virginias and Va/Per seem to come up really well in medium or smaller pipes and sometimes in conical bowls. But there are not hard and fast rules. Like Harrison, I used to think small pipes were some kind of toys or souvenirs, but then fishnbanjo put me onto them, and I tried one. You can get a good long smoke out of flake/cube/twist in a small pipe. They are great for sampling, short smokes, and getting the range on full-strength leaf before you plunge in with a big bowl (I've done that too, exhilarating but sometimes ill advised). I think foggymountain has gone with some smaller Dunhills, notable princes, in recent years. I like a variety of sizes. Plenty of medium size, some good giants, and a few small ones including small cobs. Finally, you do this by trial and error. Some pipes that you wouldn't pair with, say, an English blend turn out to be great for that. So it's mostly knowing your own pipes and trying different blends.