I'd say it's about time to strain and mix in the simple syrup....I hope you've made already. *grin*
I followed your and Gwydion's recipes, they are very similar...I used Sorrento lemon from a import friend of mine...I used 18...I zested the lemons...this is the 8th day and the zest are totally white now and the alcohol is a very deep yellow. I have been gently shaking the mix once every day...will keep an update..
There is no doubt in my mind that you used plenty of lemon. Good luck!