Block girdles, yay or nay

Can a non splayed 4 bolt cap be used? Wouldn't it be a good idea to have the block align honed and have the entire assembly balanced? One thing that I've never seen on here is having the crankshaft checked for being straight, maybe because that's second nature to you guys. I read earlier on this post about using aluminium main caps? I don't think that is a good idea.
Why not on aluminum caps? They act as a cushion if you run into detonation problems. Same thing with aluminum rods