Hello Alistair, good question, I can't wait to hear more opinions.
In my current mix of FFOF, I add a 16 oz cup of perlite to 4 gallons of soil, not much really. With plants in 5 gallons of soil, my containers are light and ready for water every 3 days. Seems like I'm getting decent aeration and it doesn't pack down too badly. I stir up the top inch or two and level it out before watering also. I'm definitely still working on my medium so take my opinion with a grain of salt :ignore: