I'm looking into knitting these slipper socks http://www.patonsyarns.com/pattern.php?PID=2701 but I want to use a chunky/bulky yarn instead (like WoolEase Chunky, something thick and cheap to experiment with). I think the gauge will be off, obviously. I know this will result in a bigger finished product, but is there a way to figure out -how much- bigger? The pattern states there are sizes at the beginning but in the pattern itself there is no difference in stitch numbers or anything. I -want- to make sure it is a little bigger since I bet my legs are a bit thicker than most. Since it is cuff down, should I just experiment by knitting a few rounds and seeing if it will fit my leg? Or is there a smarter way to do this?

I'd find a slipper sock pattern that calls for chunky yarn. Something like this, maybe: http://www.lionbrand.com/patterns/kwetq-scrunchySocks.html?noImages=

These are really easy and knit up super quick.

Those are beautiful! You could just try making a smaller size and make them longer, but no guarantees it'll work. It's just a cost issue they are just worsted weight yarn. There are lots of inexpensive worsteds out there to use. The Patons Classic Wool called for in the pattern isn't really expensive either.