Why's that?
he might mean that if you dont know how to program 3d models already, no ones gonna really be able to just tell you how in one post...
i know what you mean about the arch piece. its a very good and functional brick. you could make one out of different slopes though. start with a straight one, then use a -72 degree one on top of that, then go to -45, then -25 then flatten out to horizontal, and do the same on the other side! :D
still not round, but not as blocky as using all squares. :)