a51 190 distance question

I'm attempting to get successful grow going now and I feel ive always had light-distance issues.
I read the par readings and im confused about how many umoles a plant utilizes at which state in its life (seedlings, vege, late flower etc.)

So my set up is a 2'x2'x4.5', with a XGS -190, and i plan to have 2 plants, and i wish to utilize my height and surface area.

My question is, how far should the light be from seedlings? vegging plants? flowering plants?

Also, can I use the distance of the light to cause a stretch or so to help utilize my area? (forcing it to reach, or closer to stimulate horizontal growth or photosynthesis or something?

from area51 description. We recommend 30" above seedlings in 100w mode, 20"-30" above vegging plants in 100w mode, and then 18"-24" above flowering plants in 195w mode.

Thanks for the reply. I also came across that onthe updated site since i last checked.

Anyone know the answer to my more biological question? Or would you say doing those heights properly would properly utilize my growig space?

Yes you can just like any light if it is too high up it will make the plants stretch.

The plants will tell you what u need to know,
look for stretching and stress. But if they are pointing to the lights and looking healthy, ur all good. I have my sg190 about 20" from canopy

Thanks for your response.
Its just that my last grow was tiny and didnt utilize my grow area at all, and left with tiny useless plants. I believe that throughout their lives their lights were too close, not stimulating and vertical growth.

Check my grow out, might be similar to what your doing, just did a video update