Has anyone tried this?

[DecepticonDon]

even though there is some restriction in the headstock area, I think the Triumph engineers would have calculated this into the equation(s) for airbox tuning. This tuning however, is optimized for a certain RPM range. For a street machine this is almost always a compromise. without a bunch of physics calculations, you simply wouldn't know at what range this tuning is for.
You also wouldn't be able to tell how many gains(or losses) your modifications yield without before/after dyno time.