BTW i confirm that dng are 4680x3498 as expected (without the "DNG Recover Edges" pass)
FWIW, there are two sizes defined in the DNG:
1) "default crop", which should be the same size as the largest jpeg
2) "active area", which should be all the pixels that contain image data.
Which one is used depends on the DNG processing software.
Also while the "default crop" is the same resolution as the jpeg, it generally does not contain the same image, for two reasons:
1) The canon firmware may do significant distortion correction on the jpeg, so the final pixels on the jpeg don't correspond exactly to pixels in the raw data
2) CHDK makes the default crop centered on the sensor active area, while the firmware may use a different location.