I am in the habit of only slipping the first stitch in an SSK -- I read somewhere that it makes for a neater counterpart to k2tog that way. It makes for a much, much trickier decrease if the second stitch is a yo, and it took me a big chunk of the leg to figure that out.

If you need more length in the feet, you can keep right on going on the opposite foot chart, just using the outlined box to show you where you are.

I should have added one more pattern repeat for my son with his big pre-man-sized feet.