There is a nice article in the Countrygardens.com blog section on just this topic. Do the 8' sections have the 'top end' or is that what you rooted. Anyhow, you could end up with a nunmber of cuttings to offer for trade and
I ended up chopping up my 10+ foot Santa Rosa trunk last year before I saw this info and immediately thought "doggonit, that would have been the perfect thing to do".
good luck,
Will

Your original cutting must have been from below the Y. I wouldn't cut it again yet. Some of them like naughty nick, NOL, MADM etc like to get tall before they bloom.
If you whack them before they make a Y they might just keep on growing until they get to the height they want before blooming.
I would try to keep it in a nice large pot and feed it some bloom booster until it Y'd. Once you get the Y at the top and it flowers you can always cut off the top at the length you want to make a nice sized tree.
I have found with some of the taller growing ones, if you put them in the ground they will grow and grow before they bloom. Same thing with seedlings...keep them in pots, they bloom sooner than the ground. Just my opinion.