For those that use a K&N filter on their CAI's. Is there a certain style ie. round-tapered, and size this a is preferable?

I was just browsing around on K&N site and the CAI tube I might get is 2.5" so the filter I was looking at would be something like:
5-1/2 base dia, 4-1/2 top dia, 5 long, Centered offset, part no. RC-4670

How big is to big or too long before it doesn't fit in front of the wheel well? And should one get a centered offset or a canted offset? Also price....the retail sites I've looked at so far average like $47-50.

 

Just get 2.5" k&n cone filter...On a cold air intake, I dont think the filter can be too wide cause it has to go through the hole to the fender...

 

The smallest cone filter they have for a 2 1/2" flange is:
4-1/2 base dia, 4 top dia, 3-13/16 long.

Hows about a round-straight? Anyone use those?
2-1/2 flange, 3-1/2 dia, 4 long.