A couple of people on the Pos .Net forum have been struggling with signature capture devices, specifically where the captured signature is skewed when drawn from the point data returned by the device. It turns out there are several ways of converting the data from the devices into the point data returned by Pos .Net and not all devices use the same one. The Ingenico device apparently requires a specific setting, and others may do as well.
There is no way of setting this via the common Pos .Net interfaces, but luckily there is a solution which has been posted here by Sylvester (one of the Windows Embedded Team members).
Sylvester has also posted another useful (but distressing) tip for handling cancelling of the signature capture process.