I am using 75 watt equivalency bulbs on my plants, and I don't like my plants any closer than 4 inches. At double the power of my bulb you need a greater distance. Since light spreads in two dimensions as It's distance increase in one dimension you need to multiply the square root 150/75 times 4 inche to have the same intensity that I have on my plants. Hear are some picture of what has worked well for me.

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This is my 4 ft square with peppers

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Seed grown meiwa kumquat tree next to is bucket light system---1 bulb

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Light for broccoli below, heat for meiwa kumquat tree roots above.

While there probably nothing here that is what you are doing, it shows about how close you can be. Some plants scald easier than other. Most plant will show signs of distress before any damage sets in.