really, you need some sort of trumpet inside the filter, otherwise performance wise you'll go backwards. get some rubber elbows from a sc/gt or hm 1000/1100 and fit some trumpets like the tpo or corse dynamics ones. you'll need much bigger id pods then.
There's a write-up out there somewhere about using the velocity stacks from the stock hyper airbox. I got one off ebay for $25 shipped and am waiting on K&N cone filters to arrive. I'll need to get some 80 degree bends to get the velocity stack/filter to fit under the tank properly, but once it's in there, it leaves plenty of room for battery, coils, and main harness relocation.
Throttle body inlet is 2" OD. Here's a quick write up of what I did, total cost was around $100
Airbox from any Hypermotard ($25 on ebay). Pull the plastic velocity stacks from the bottom and trim off the mounting collar. I just scored it with a utility knife and snapped it off. Clean up any remaining bits with utility knife.
2 K&N RC-9420 ($50 each from Advance Auto, but I used a 40% off $100 coupon) This model has a breather hole pre made and offset inlet. Actually ordered by mistake, but the offset inlet allows the filter to be rotated to easily get the best position.
2 Silcone elbows 90 degree 2" to 2.5" ($7.75 ea on Amazon). I got the 2" to 2.25" and they run just a bit small so I had to trim the end of the velocity stack in order to get the hose on. I would go with the larger diameter to save the trouble. I trimmed down a fair amount off of each hose to get the tightest possible fit. On the lower, I cut back to the start of the bend so it would tuck in a bit more. I fit and trimmed about three times and finally got it where I wanted.
4 stainless hose clamps. K&N comes with one each.
Picture shows them mounted before I trimmed another inch from the TB side of the right one and before I trimmed into the bend of the TB side of the left. Just have to run a breather hose to one of them and fab up a mount for battery and coils.