we plan on doing either 30G or 20G (probably 30). I always brew with a buddy so we never do less than 11G batches now.
I almost don't want my buddy to sell it because that MT is perfect for big grain bills for 99% of AG batches for 11G size (obviously perfect for the 5g batches too).
Only once did I have trouble fitting the grain and grist into the tun on an 11G batch (but the grain bill was almost 50lbs). It was a huge HUGE RIS with a 48lbgrain bill (I might brew 1 of those a year). It still fit, but it was to the rim. For any batch under 42-45lbs you have plenty of room to stir without spilling. As a reference most 11G batches for IPAs or strongs like Denny's rye smile or arrogant bastard, etc. are in the 35 is lbs range. i.e. unless you are doing a ridiculous 1.100 SG batch it won't be an issue.