if you have a digital timer ( if you dont their pretty cheap) you could set it for longer than twelve hours on say 24hr on twelve off that way 11 days turn into 5 1/2. your babies dont care how long the day is for flowering just as long as their getting their 12 hrs of darkness. not only do you strech out the flowering cycle to cover your trip but your buds are also growing bigger while your gone. make sure ou have a little extra room incase the extra long days strech them a little. shouldnt happen though because their already in flowering.enjoy your trip and let me know how it goes!!!!