We bought some bare root Sawtooth oak seedlings from the state nursery late last February and planted in early March. We bought 3' cheap roll up tree tubes that are solid with no vent holes and also bought some 3' mesh tree tubes. I planted most all the sawtooths in solid tubes thinking there is no way they would grow out of them by end of summer... I was wrong... I ended up having to stack tubes. I am 6'2" and this one is up to my chin...
They do grow really fast in tubes... noticed grasshoppers are eating several of the leaves off mine in the tubes... walk past a tube and it sounds like someone rattling a can of rocks with them jumping around in the tubes...
Good thing you extended those tubes. I went out on the porch at the farm several years ago at night to take a leak and there was a doe, on her back legs, eating the main leader out of one of mine that was growing out of a 60" tube.