The best way would be to get yourself a light sensor to measure what the canopy is getting. Or a temperature meter to measure the temp of canopy leaves.

Put the back of your hand at canopy height and hold it there for 30s-1 min. If it feels uncomfortable then raise and try again. To tell if it’s too close

Putting a massive light on a tiny plant you can run into issues of burning the tops and/or super drying out the top layer, so be mindful when watering.