We have talked on our suction conveyor very often.It is good at transporting paper and films.
Yet its belt surface is always flat due to a flat belt and suction.
It is just like platen, rotating platen.
In general belt surface fluctuation in Z direction is within 50 microns while the belt is rotating.
This is the best tool for continuous inspection by camera or laser.
Please look at belt surface in this video.
Dymco metal belt suction conveyor page:
Steel belt video: http://www.youtube.com/results?search_query=dymcooverseas&sm=12
DYMCO, LTD URL http://www.steelbelt.jp