has anyone thought of using a filter with some "legs" to space it off? even a small piece of gauze-type or foam type filter could work well? this would allow the filter to be inside the "mouth" of the smooth airflow.
dammit i love the looks of stacks so bad, but i've heard nothing but horror stories about tuning them and getting them to run well like a factory airbox... 
The best single stack filter, as Turboguzzi pointed out, is a sock. The problem is the look, in that they cover the whole stack, and use zip ties to hold them on. A secondary issue is clearance. A sock on #2 can potentially foul on the 77/78 throttle bell crank, which is why I rejected that easy solution. The best solution for our cafes is a single filter mounted across all four stacks. The problem has been finding one that not only looks good, but actually works.
wannabridin - I think you are mixing the air box vs pods issue, with using stacks. When people remove the air box, and install pods, one of the essential things they remove is the stock stacks. These are an integral part of Honda's tuning of the intake system, and pods do nothing to re balance the system. There have been a number of members who have removed the air box, but retained the plenum & stacks, and fitted a K&N on the back. As far as I know none of them experienced the same tuning issues as those who only used pods. bwaller's BOTM 590 uses this setup. His only comment has been that he can only get 115 out of it, because the stock plenum eventually restricts air flow. So the next step would be to remove this restriction, and just filter the stacks. This is what I am doing. So by all means use stacks, just make sure they're right for your application, and not bling with headaches.
Some thing to think about - the only time there is
still air in an air box, is when the engine isn't running; the rest of the time it's about managing air flow.
