I don't know that you need to make it any bigger. I've used a 4" flex alum. air intake pipe from the front fender opening on my '94 (leaving enough room for air to reach the power steering oil cooler) and then clipped in place below the filter. On my '93 I used the 5" corugated black plastic drain pipe in the same way.
I have plans for making an air box over the K&N using alum. diamond plate; but at the moment I have a straight piece of heavy gauge alum (about 8"x10") as a heat/fan/clutch dust shield between the compressor and the filter area; with some foam pipe insulation on top. It's worked so well I don't know whether I'd bother with building a box. One alternate is the shield made by MagnumPowers, which also incorporates a bracket for the MAF. About $100 I believe.
Jim.