Friday's puzzler for you caffeine geeks: why does a vac pot seem to require consistent up dosing to brew a good cup? I tried SCAA cupping standard ratios, and the brew tasted acrid and over-brewed. Upping the dose to 11.5g per 150ml (40% up dose) produced much more satisfactory results.
My own two cents: The bottom-up agitation combined with top dumping of the coffee means the coffee is particularly hard to mix into the water consistently throughout the relatively short brew cycle. If it takes 20-30 sec to wet all the coffee, that's 25% of the brew cycle. A higher dose may be a shortcut to better brewing ratios from the start.