The difference with the 6.5 is that the ratio of dead space to batch size is very high. For example, if I want to make a 2.75 gallon batch (fermenter volume), I need a total of about 4.3 gallons for BIAB, per my profile. When I pour 4.3 gallons into the 6.5, over half of that ( ~ 2.5 gal)...