We analyse the global structure of the old stellar discs in 34 edge-on spiral galaxies .
The radial and vertical exponential scale parameters of the discs are obtained by applying an improved two-dimensional decomposition technique to our I -band photometry .
We find a clear increase in the disc scaleheight with maximum rotational velocity , in accordance with observations of the stellar velocity dispersions in galaxy discs .
The range and maximum of the intrinsic flattening of the disc light seem to increase with both maximum rotational velocity and total H i mass .
We use the disc flattening to estimate the disc contribution to the maximum rotational velocity , resulting in an average of 57 \pm 22 percent .
The disc light distributions are further investigated for the presence of radial truncations .
We find that the radial light distributions of at least 20 spirals are truncated , corresponding to 60 percent of the sample .
For small scalelength spirals , which are the most numerous in the local Universe , the results suggest that the average ratio of disc truncation radius to disc scalelength is at least four .