@Trala
So here is something that many growers on this site may find controversial. You may love it!
You mentioned that you would like to achieve closer internodal spacing. It is possible to stunt height without stunting growth by providing almost too much light AND almost too much nutrient concentration in an effort to create a massive amount of roots. The photos below are of plants that broke the surface on November 2nd. Yes, they are only thirteen days old. These are regular photoperiods so I will only keep the largest female. I will be topping them tomorrow and sending the tops out for DNA sex testing. They are currently producing 9 - 11 finger fan leaves.
The photo below shows that the tallest part of the plant is six inches tall (ruler in back). The top leaves are node #9.
I put a pencil next to the trunk for scale in the next photo. The photo shows the ribbing on the trunk and branches. This will add massive strength to everything that follows. Also notice that the photo shows four nodes in the first two inches of plant growth. This spacing will continue throughout the grow.
This method requires light height adjustment as many as three or four times per day initially, until there is enough root mass to accommodate the amount of light. It also requires early addition of CalMag and MSA (mono silicic acid)(silicon).
They are currently receiving 392 watts of light (130 watts - 227 watts the first week). No added CO2.
The current ppm is 1300 (part of this is pH adj. and CalMag). Chart recommendation for a one to two week old plant is 500 ppm. They received the 500 ppm since birth. The chart recommends 900 ppm for the third and fourth week.
P.S. I had some open baskets (for a little while) so I put in a couple of Cayennes. It turns out that the net cups fit perfectly in a wide mouth Mason jar so I'm going to try a modified Kratky with them.
️Happy Humpday Growstars 
