Howdy. What you're planning is totally fine. A single 4 foot FL, full spectrum won't be too much light. Keep it at 24-30" above seedlings and it should be all good. I suggest just rigging it up for easy adjustability. As you go along, just observe them and see if the lighting is adequate. Stretching and lanky-Too far. Cupping or burning-to close. It might take a couple days to find your sweet spot, and it will probably change as they grow. Minor adjustments will keep everything even and tight. You'll find the spot, I gaurantee it๐๐