Yes, thank you!  That's really great.  However, I'll look through the `ImageCorrFunc` stuff again to check that it's not there that `Quintic` (the default k-space interpolant for `InterpolatedImage` objects used by `_CorrFunc`...) is being used a lot. In these tests, are the sizes of region being padded is not varying from image to image, correct?

The only place I thought would be where `Quintic` might be happening is within the `applyNoiseTo` method if the the size of the input/output image keeps changing (i.e. the image for which it needs to apply noise).  In this case the correlation function needs to draw itself a number of times over different grids to keep generating random realizations from the power spectrum: if these grids were constant size the array we require is stored in the `cf._rootps_store`.  Hmmmm, I'll take a look...