I have thought about placing the LEDs in a tube appropriately sized to the size of the plant.
Line inside cardboard tube with mylar.
Drill holes in tube. A symmetrical pattern evenly space
Place cap with hole pattern on top.
Add venting for air movement.
Keep the heat of the power supply out of the growing area.
LEDs inserted in to holes and wired from the outside of the tube.
Place tube over plant.
To keep LEDs close as possible start flowering immediately.
You would need one for each plant.
Could be cone shaped.
Probably cost too much.