I brewed a 100% GP ale earlier this year and got 30.66 PPG (9 lbs. of GP yielded 6 gallons post-boil of 1.046 wort).
Thanks however I am little confused. Most lighter base malts seem to be around 37 ppg or 80% yield. You got 30.66 ppg from GP which works out to 67% yield? Sorry for my lack of comprehension.
EDIT - I appear to not be using the correct terminology. I think I may have found something that cleared up my confusion. It seems that those figures work out to near 36 ppg or 78% yield in regards to the terms that I am recalling off the top of my head. Thanks!