I'm looking at moving to a 3V setup from a Grainfather as I'm finding efficiencies too difficult for higher grainbills. I'm not sure how to determine the vessel sizes I should go for. I'd like to be able to brew up to 70 litres at a time so when I look at systems like SSBrew Tech they have a 75 litre option, so I'm assuming I'd go for the 75 litre boiler, but for a mash with grain and strike water only that is going to be way less than 75 litres and with 3V processes I've seen first hand the mash water drains into the boiler whilst sparging so what capacity mash tun would be required?