157 is a pretty high mash temp for easily fermentable sugars. Also the crystal malts aren't going to be as good at producing easily fermentable sugars like your base malt does. I also think WLP001 has a tough time doing hard work at 62.
My opinion is that 1.020 might be all you're gonna get. I bet it still tastes good.
Bottled: House Stout, Greenbriar Session IPA, Arsenal ESB
On Deck: Death by Hops Clone