I'm looking at buying a conical and I have some questions that relate to head space. I'd like to get the largest fermenter I can afford. Right now it's looking like I could swing a 27 gallon unit. My question is can I ferment 5 gallon batches in this unit? I think 5gallons make for good test batches. My concerns are:
1. head space and oxidation - I've read different accounts, some say it's going to fill with CO2 and it's not an issue for primary, others say leaving kraussen that would otherwise be blown out a blow off tube contributes to off-flavors.
2. Physical shape - with a small amount of beer, will I loose a large volume to the shape of the conical when I go to collect yeast / trub?
3. What about using it as a secondary? Can I hit it with a shot of C02 to fill the head space?
Any input is appreciated!