A modified filler composition used in papermaking is provided. This collimator sampling is accomplished through strategic placement of the detector heads relative to each other such that for any given projection, a complete imaging of the projection is acquired by summing the complementary contributions of the multiple detector heads at the projection under consideration. In some examples, an example vehicle-actuated mechanism disclosed herein forces a compressible seal down against the vehicle’s roof and maintains a compressive sealing force over a range of roof heights and positions.