I'm ramping up my wine making this year and have started to plan and
buy equipment. I've been making batches of 5-7 gallons of wine to this
point. I plan to make around 30 gallons.

I have a large 55gal food-grade plastic barrel for primary and a new
30gal oak barrel for aging. My question is what others are using for
secondary/MLF containers.

At 30gal it isn't too unreasonable to have 6 carboys sitting around
(and I already have 3). But I've also thought about SS 15gal beer
kegs. What do others use for larger-volume secondary containers? What
do those who make full 55gal barrels of wine use?

Thanks in advance.

-Greg