have been doing extract brewing and steeping speciality grains. But i would to try mashing some grains. have built a mash tun out of a esky with a copper manifold.my question is when you start mashing how do you calcalate how much extract to use My normal recipe would use 2500gr malt light extract 75g crystal malted grain &500g dextrose.so if mashed 2kilos of pale malt how much of the extract&dextrose would i cut out