question about lighting

i've got the htgsupply.com grow tent (large size) its 70 inches high and 40 inches out each way.. it comes with ducting to attach the MH/HPS light to which forces it to be very high up.. i've raised the plants about 2 feet, which is making them about 4.5 feet from the light.. they seem to be growing very nice and densely..

is this ok to keep this setup like this?

i dont have an actual pic of my setup but here is one of the tent but here is an example on how it is forced to be so high up

im thinking its not a problem since so much light is reflecting in such a small space

i don't know what wattage your light is but for a 400w HPS it needs to be 20 inches from plants, so a 250w HPS 10/15 inches get the drift man good luck with the grow