we worked it out once by measuring up the aeroplane.
for this type of aeroplane...
weight 590 kg
lift 590 kg
thrust 64kg
tail download 37.6kg in cruise.
depending on the speed and position of the cg, the tail download varied between 37kg and 63 kg.
to fly my aircraft (similar but not the one in the photo) at Vne in straight and level flight requires full forward elevator (so obviously an upload) to get enough incidence off the wing.
ymmv.