you can use hps all the way through but in real terms to the plant its not the best thing to do, the mh bulb reflects spring and the hps summer. when you veg with mh you will see much more growth of the leaves and a better shape on the plant, also it will take a lot longer for the plant to adjust to the flowering 12/12 because it will be already used to the summer light and it will take longer for it too adjust. i had the 150w and 90w ufo on four of my plants and the 2 that were nearer the hps have tall lanky stems with no foliage growth, the plant is all bunched into itself, the 2 plants that were near the 6500k ufo are much healthier plants and they have gone into flower about a hell of a lot quicker.
i will always use metal halide/ufo 6500k for veg as you get better results, its the best of both worlds and anyone who is going to be going to be growing full time will see the benefit of vegging with mh staright away. they only cost 25 quid and the ballasts nowadays take both types of bulbs, get yourself to the growshop JINGLE and get yourself a metal halide bulb, you may even find one cheaper at a security lighting place as thats what they are used for. even vegging with a cfl 6500k would give you better results.
this is just my opinion, its like saying can you run a car on farts, you can but it will be slow as fuck. petrol is better.lol!
WILLOCO, they are looking nice fella, just keep using the grow nutes until 2 weeks into flower until you start seeing first buds and then start using the 1ml of the bloom nutes. you wont believe it but i am using the same girls clothes hangar, tent, clip lights, fan which i took apart and cut smaller. i am even using the same shitty coloured brown dunnes towel and the b and q pots you have, nearly identical set up.
its mad the crap you end up using when you grow these plants.
JAY im not saying your wrong in what your saying its just i dont think its best, do u not see great growth with the metal halide. theres no reason not to use one today as they are cheap and if you already have the ballast you may aswell get the bulb.
later
lu