yes 11/13 os 11 on /13 off, i have 2 600 watt lamps which are on easy rollers. i am able to lower one light and keep the other up for my taller plants. making sure that all my plants get enuff light . the bulbs i am using are growlux dual spectrum bulb the give out an amazing 95000 lumens each so i have little problem with light averaging near 75 watts per square foot. i also have the room lined with mylar which reflects up 95% of the light as well. what i would advise u to do instead of pulling up a shelf , just to set ur plants on sumthing untill they are tall enuff to place on the ground along with the rest . if u do put a shelf up make sure ur able to fold it down when ur clones get up . this way ur not wasting any grow space u might have. i like for the first 4 or 5 days in the flowering to keep the light as far away as possible to allow the plants to get used to the HID then i lower the 600 watts down to about 24 inches from the tops . i leave my fan also blowing up into the light which i think helps keep the tops from getting too warm. yeah and i do use a cloning dome but not a heat mat . i found with the heat mat alot of my clones started to get mold before they rooted . my propagater was a heated one and i ended up cutting the plug off it and using it like normal one.
i hope this helps ya mate ,
Hal