Ok so I was a bit bored and decided to get on and fit the filter, aaannndd.... I'm unimpressed.
It barely seals to the ring inside the airbox, and with the lever in place I can quite easily move the filter with my hand. There are also key differences in the moulding of the filter compared to the OE Part.
The OE Part has hard plastic ends, and at the sealing end the ridged ring is much thicker. The Pipercross part, both ends are rubber which flex, and at the sealing end the ridge is thinner. The sealing ring on the air box has two grooves in it, the OE Part seals to both grooves, where as the Pipercross merely touches the inner groove.
When replacing the lever to seal the OE Part you can see the pipe/box move due to the pressure involved.
It could maybe seal ok if I put a thickness of plastic between the filter and the lever to exert more pressure, but I don't feel comfortable with that. Nor should I have to do it.
Needless to say I've put the OE Part back on. IMO the sealing end of the pipercross needs be changed to mimic the OE Part better.