I just brewed this, thanks for the recipe.
I only did 3 modifications:
First, a 3 step mash, which lasted around 70 minutes.
Second, as I use Kg and Gr (metric), I rounded up a bit the quantities.
Instead of 4.8Kg and 450gr grain, I used 5Kg and 500gr.
I got 20L at 1062 and according to Beersmith it's 70%eff, which surprises me as I usually get around 60-65. Maybe it's because of the mash.
In any case, I'll post how it turns out in about 6-8 weeks, after fermentation, resting, and bottling.