Could someone give me a little insight of how far above I should have this light?

If you have a dimmer, you'll want it fairly low power and nice and close to short plants -- this will save you money but is going to need some trial and error if you want to work it out. In general this shape of light should be anywhere from 12-18" away depending on the power... if you want to eke out a bit more coverage you mgiht want a bit more height. The hanging distance should primarily be about properly covering the full area of your garden. The PAR maps they often give with lights can help choose what is best. The 16" map looks damn good for 12/12 in a 3x3 for ambient CO2 -- So 16-18" at 100% for flower. Now, if you keep the same hanging distnace, that makes calculating for vege easy. if using a 18/6 cycle, it is 2/3rds of the power compared to 12 hours. So, 67% @16-18" will do you good. You still need to adjust to what you see. This will get you close, but the environment and the plant dictate the specifics, whcih will vary from one garden to the next. As far as seedlings, the first 1-2 days tehy don't need much, but they quickly need more. I'm usually giving near full power by day 2-3 or i get stretchy seedlings. Use resulting internode length to guage your light intensity. If too tight, need less, if too lanky, need more. Simple as that. If you want to save watts, low power and close distances is a good idea for any short-stature plants. Doing this does save watts, but reduces depth of "good" light, due to the spread of light adhering to the inverse square law. So, when it comes to a larger plant and especially in flower, don't get hung up on how close you can get it... the hanging distance should be about geometry and proper coverage out to edges and corners without sacrificing too much in middle (overall average the most anergy applied possible across canopy, without causing damage) -- trial and error to fine tune it.. These are good places to start. example -- i have 1 colas that is 2" taller than the rest... it's experiencign a little light bleaching.. i know i'm right on that edge relative to my local environmental variables. No damage below that line and took several weeks to occur (slow moving = slightly too much). what you see can inform you about your decisions.. what you see should be the final say in what you do with the light.