When to flower your plant... The first consideration is your vertical space..
The second consideration is your LIGHTING..
The third consideration is, the number of plants you have...

If you have only one plant and you are using a 400-1000 watt HPS, you should top your plant(make clones) when your plant is 12-24 inches tall..
Then let you plant grow for 7-14 days (18+ hours of light) and then flower it (12/12)..

You will grow a tremendous plant... that will double in size.. maybe a bit more than double.. especially if you don't have the light close enough (your plant will stretch)

The more plants you have (or less light you have), the less light penetration you will get to the lower foilage. So, you will want to flower them when they are shorter. LIGHT is EVERYTHING.. every inch your foilage is farther from your plants will directly effect your yield. An HID light that is more than 12 inches from the foilage is a MISTAKE!!!! A JOKE!!!
A WASTE!!! a disgrace

i love you

Plants double and sometimes triple in size when flowered. When they start passing 2 X's there vegging height... that is a sign that the light is to far away and that the plant is stretching.. This will have an adverse effect on all colas.. all nugs.. all buds..

: (

BTW - NICE plant

love