Think Hydro dynamics if you must. Yes the bends in the pipe will restrict airflow, but when you have air moveing at high speed entering the intake of the snorkel, and forceing agaisnt the air that is slowed down in the tube what will happen? Will the slow air cause a space fluxed, and reject the other air sending the snorkel into the past? NO! its a simple theory.... Air will push past the bends, and continue to flow nice and fast. If its such a bid deal stick a peice of 3" PVC out the front of your jeep as a snorkel.
As far as building your own snorkel. I am going to be building one and hopfully if I can designin it well enough will go into the cab up the front pillar ( Made from metal) and have a small scoop on the roof. I had the idea play GTA san adreas modding a car, and am still trying to design it which is proveing rather hard lol.