Hood clearance can be an issue. You don't want anything too tall. But if the filter is too short, the top of the air horn is very close to the top of the air cleaner; and that restricts flow.
The "Tea Strainer" air cleaners will keep out the big bugs and rocks, and that's about it. I got the bright idea of cutting up a K&N filter and replacing the foam in the tea strainer with gauze elements. Bad idea. The engine ate two of them.
On the street I use these oval air cleaners. The stacks are removed, and the base bolts on to the top of the valves, using the existing holes. They do cost some power over the stacks. But that power loss is at the top end.
I also saw this on a car a year or two ago. I think it cam from TWM, but I didn't get a chance to talk with the owner about it.
