Evenin major, was just re reading your post talking of raised beds and so on,...if i was you i would look into using "Rootbuilder" sheets! You can choose the size brotha. When it's time , ya just cut a few ties, and unwrap the 100 ? gal. pot. They use them alot over seas in the larger nurseries for their ease of transplanting. All they do is cut of the wrap and put another pc . in, fill up the void with new soil...done .It would look like my 26ers but 5 times as large....yowsa ! Lottsa soil....big plants, plus , like you say, if they like the soil below , great, if not, doesn't matter much. Anyhow , just a thought for ya pal! Cheers.