i actually did a test last year with 8 clones using a 400watt HPS grolux (flowering bulb) and guess what? they all grew 'really' tall infact about 3ft tall in only a few weeks. after i began to flower them i was forever having to top them because they kept growing and growing and growing but it was all stick and few nodes.
from my little experiment i find its best to use anything that is ultra high in the blue and red spectrum and let them veg for as long as posible to keep them short and grow shed loads of more nodes. more nodes = more bud :jointsmile:
allowing them to veg just an extra week or more can really make a huge difference to the ensd result bit i top mine all the time while in veg to promote more nodes to grow while its as short as posible.