Some years ago I planted a small kumquat behind our house, but it was not a great success. We have a friend who looks after our house when we are not there, he cut away the dead top, trimmed the trunk, and we now have a beautiful little Seville orange tree, which the kumquat had been grafted on. With a little bit of ‘hear cut’ it will make a perfect lollipop tree which is nice all the year round and which is also producing fruit which I use for making tasty marmalade.
I have also seen them used in Thessaloniki, the trunks have been trimmed naked up to around 2 1/2 m, I would guess.