Member of the Month: Feb 2014 - Plant of the Month: June 2015
Happy Skunkday Solo
Most people change to 12/12 depending on how much space they have left in the grow room. A typical sativa plant will grow 2-3x the size it was in veg when switched to flower, and an indica will grow 1.5-2x. Those numbers are very rough estimates though, as you can contain the plant with various growing methods (for example how you're scrogging).
Another way to tell if your plants are 'ready to flower' is if they are showing alternating nodes (the nodes are no longer parallel) or if it is showing pre-flowers. That is usually nature's way of saying they are ready for 12/12.
I would say, if you think you still have the space then keep on vegging! Nothing wrong with it. I've read numerous journals where vegging an extra 1-2 weeks really impacted the end yield weight.
I was personally going to switch my plants to 12/12 almost two weeks ago, and I am really glad I let them veg a little longer. Not only are the side shoots starting to catch up to the top (to make more of a candelabra), but I have pre-flowers on all of my plants now.
When you are tying your plants down, are you using an anchor? Not sure what you mean by "it causes problems with my net cups" but if they are being pulled out/sideways by the force of the plant, there may not be enough force holding the plant to the pot.
If the stem is being bent in one direction, it needs an "anchor" to hold it in the direction it originally wanted to go, especially when the plants are big.
There are some pictures on this thread that show how to make sure the plant is anchored. (control+f search "anchor")
How early can you start Low Stress Training - LST?
In those pictures, you will see the red wire is acting against the force of the black wire which is doing all of the bending.