what you refer to as stretching is actually normal rate of growth. plants use the energy they get best on a 16 hour day light cycle because they store that light energy and do most of their growing in the 8 hour night. they dont stretch for light during dark periods, they build themselves then.
~example~
plants on 12/12 are flowering and making additional growth hormones within themselves,+ longer night for more time to used stored energy and grow,= plant getting way bigger during flowering.
but leaving lights on will make plants smaller and more bushy because they dont grow nearly as quicklly. I prefer to use the FIM method and leave them on for a 20 hour day period/4 hour night. Gives twice as many bud spots from the FIMming and nodes stay a half of what they would be on a 16/8 timer
anyone else agree with this?????