The size of the Cardassian Hideki class

The Hideki class was a warp-capable multipurpose starship used by the Cardassian Union's military during the late 24th century.

The Hideki class was originally designed as a small Shuttle. 

design sketch by Jim Martin

screencapture by trekcore.com (DS9 "Profit and Loss")

Later, the Hideki class was used as a attack ship. Visual Effects Supervisor David Stipes has stated that an overall length of 500 feet (150 meters) was generally used onscreen. The Deep Space Nine Technical Manual gives us a Length of 85.78m.

Distances can be measured by means of the physical laws of optics.
For that I have made a calculation using the vanishing point in the screenshots of the Dominion battles.
With the help of the red lines, I have chosen two corner points on the Galor class, which are exactly opposite. Where the lines intersect lies the vanishing point.
To calculate the length, the yellow lines (starting from the vanishing point) must run to the bow and stern of the Hideki class. The Hideki class should be almost at the same angle and elevation to the Galor class.
The yellow lines now mark an area on the Galor class. This area is the length of the Hideki class, if the ship would fly directly above the Galor class.

screencapture by trekcore.com (DS9 "Sacrifice of Angels")

I made another measurement from a differen episode to confirm my result.

screencapture by trekcore.com (DS9 "Sacrifice of Angels")

If you extend the marked areas of the Hideki class to the position of the Galor class (484m length) with the help of lines, you will get a length of 140.2m for the Hideki class in both measurements.

foto by max.klanky.com