Gone For 2 Weeks, Need Helllp!

so here is my current situation. I'm going to be gone for about 2 and a half weeks. My current static flow system only holds 3 gallons and I was afraid that it might run out of water by the time i get back. SOooooooo..... I put the top on a new 10 gallon bucket and filled it with water. I added another airstone and another pump to it. I put 8 gallons in it so far and its not completely to the top. But, I cant fill it to the top cause it has 2 little holes toward the top of the bucket.

Now, #1 since the rockwool wont be in water the whole time, will that be a problem? the water level is eventually going to lower a little bit. the roots are always going to be soaked in water, but i dont know if this is a big deal if the rockwoll is?

#2. how HIGH will i have to put up the lights so the plants wont get burned for the next 2 weeks or so? The biggest one is about 8 inches tall or so. And they are 4 weeks old. Anyone have a good estimate?

Here is a picture of the old system and the new one that i made. LET ME KNOW WHAT YA'LL THINK!
<-- old
<-- new <-- new

I don't see why the rockwool would be a problem if it doesnt stay moist, as long as the roots are in the nutrient solution. My 3.5 ft plant is good off of about 2.5 gallons for a little over a week. I imagine 8 gallons would be plenty, but as your plants uptake nutrients, the nutrient/water ratio will change.

What kind of lights are you using?