The stretching is usually lacking of light intensity related. Use reflectors to avoid it.

About your lighting: you said you are going to buy 5ft flo tubes, but you dont have 5 ft avalaible (its 1500mm). BTW, the VHO tubes are very little efficients, standard T8 triphosphor tubes are cheaper and it will give you a lot more light per watt, and if you use ellectronic ballast (buy the doubles: one ballast per 2 tubes), better efficiency.

6 tubes of 36w (4ft)would be appropiate for your space dimensions, but if heat isnt a problem, yo can put 2 or up to 4 more (with only 33cm in one dimension, tubes placed in the opposite wall can light plants from lateral very well, allowing you to grow higher plants). Put at least 4 tubes in cenital position (dont forget the reflector), and supplementary ones in the front wall, depending of the plants height you desire.