I've just been having a play with some numbers in Beersmith & wanting to stay with easy numbers (ie. multiples of bags):
150Kg GP (80.4%)
25Kg JW Munich (13.4%)
10Kg JW Amber (5.4%)
1.5Kg JW Roast Barley (0.8%)
1.5Kg EKG Pellets (assumed 5%)
In a 500L batch, this should get us into the mid-1080's with around 30 IBU & 30 EBC.
Also, we need to give some consideration to water treatment, since we're on tank water & it's effectively a blank canvas. I've measured our tank water at PH 5.4, but not sure how accurate that is, 'cos I've always had about PH 5.2-5.4 in the mash. I suggest something in the 75-100ppm range Calcium, so I can make-up a "stock" solution of CaCl & add it @ 1:100.
How's everybody with that plan?