I’m presently doing that one (or the striped socks, same pattern different yarn, but I’m using Lion Wool which should’ve made them even bigger).
Size isn’t the only problem.
I added 4 stitches and they’re still too tight. I also made them 9" to the flap, which is what my store bought wool socks are, they’re still way too short.
I take it that you figured out the problem with the way the gusset is written.
I think next time I’ll go 12"-14" before starting the flap and try at least 56 stitches.
For my 44 stitches I just distributed them evenly until I got to the flap and moved 20 to one needle. When I do a 56 stitch version I’ll make the flap 50%.
Someone gave me this site when I was having problems figuring out the gusset, it’s actually for the turn but will help you modify the pattern. http://www.socknitters.com/Tips/heels_by_the_number.htm
Here is one to give you the percentages, http://www.royea.net/formula.html