thanks for the reply Justin.
I tweaked slideshow dissolve, and this works fine.
Slideshow blinds seems to work differently, as though the image has an x axis repeat.
This gives an extra bit on the landscape images, and the portrait images are shown twice.
i have updated the files, so please use the link posted above to see what i mean.
I have deleted the wide slideshow from my examples in this case, so this isn't an issue, but thanks for the tip.