Need Help...Tuff Decision on When to start 12/12

ok, so i asked the question yesterday how long after topping can one safely go to 12/12...i went today and 2/3 of my plants are 16-18in. tall which are my Sativa/indica hybrids (WW, Bubblegum, AK-48, KC Sweet Dreams)...i topped 5 hashberry 3days ago and their only 8-10in. tall and healing...my problem is that if i wait much longer 2/3 of my crop may get too tall (their growing inches a day)...if i flower now 1/3 of the crop may suffer a big loss in terms of yield (my Hashberry plants which wont stetch much anyway) but if i wait my plants may get far too tall for my 400 watt hps (only 9sq. ft.)...what would you do?