I don't have a solution, but I did have the same problem. When I bought the bike it had a nice sturdy K&N filter. I bought a DNA filter to replace it and it was/is a very loose fit - to the extent that for the first month I would shine a torchdown inside the airbox occasionally to check it hadn't fallen out of the slots completely! 6 months on, it's still there, but I wasn't impressed with the quality compared to K&N. I've just fitted a stage 2 and it's made of the same strange rubber giving an odd seal, and compressing and deforming where the screws are tightened. I can only assume that the soft foam/rubber used by DNA is a cost-cutting thing.