Typically, sativa's can handle UV-B better than indicas. It's best to hang the lights around 3 ft over a 4 x 4 canopy and start with a 1/2 half hour each day and work your way up over the last 2-3 weeks. Most studies report you can get up to a 27% increase in resin, and I've seen side by side test results that substantiate that fact. Browning of leaves and crinkling are the 2 most common issues, but it won't hurt things in the end.