I've had a go this year at letting two shoots grow and flower, because I run out of height too. I'm hoping that this way I'll get more from the same plant before running out of height.
I've also seen something on Gardeners world that they are trying out a system where the growing shoot is nipped out after the truss -and then a side-shoot is trained upwards until there is a flower, then nipped out and another side-shoot trained upwards, etc. In theory that too is supposed to provide more trusses for the same height.
Since I can't stay on top of the toms that are trying to take over the world starting with my greenhouse, I haven't had a go at the GW training system ;D
A.