Talking weed...

[Pete]

As it grows. It can't change where the nodes are already at.

Ok... so does that equate out to mean it's probably going to have to nearly double in height to achieve that or something akin to that?

 

[Pete]

And... does anything about how dense the vegetation isn't between the branches actually indicate anything to you about the strength of lighting?

 

[umbra]

It might. Just top it. Cut the main stalk where 2 nodes meet. The stretch looks like a sativa

 

[Dogweed]

You could also try slowly adding more bloom formula to your feeding, that might promote some pre-flower as well. Also know that you dont have to wait for it to alternate before making the switch. I switch when the plants are 50% the size I want them to finish at, sometimes they're alternating sometimes they aren't.
Here is one that just started to alternate

 

[Locked]

If you don't have alternating nodes at 8 weeks yet you could have one monster tall plant. I don't think I have ever had a plant go longer than 6 weeks.

 

[cannabisismylife]

Are you saying that you have had plants in veg for 8 weeks and they are not showing preflowers? Take cuts and put them in 12/12 light.

this would do the job yea, I wonder how it went for you