I don't want a lot more work
High light always means a lot of work, compared to low light.
I think there may have been some confusion.
I misread that 70 micromoles should be enough to grow hair grass so instead of having the burst I thought an option was to keep the 4 banks open and keep it at 70 micromoles. It would be easier than dropping the light from 33 inches to 24 inches.
I now realize you said 35-40 should be enough so lowering the lights is a better solution. I am just a bit cautious of dropping the lights 9 inches from 33 to 24 inches - It sounded like a huge increase in light.
When I drop the light should I do away with the burst all together?
What I posted is, "You can see, from that chart, that at 33" you are getting about 70 micromols of PAR, which is more than enough light to grow hairgrass. If you were to use just an adjacent pair of bulbs you would get about half of that, or 35 micromols, which might be too little light. But, lower the light to about 22-24 inches from the substrate and you should have about 45-50 micromols of PAR at the substrate from the two bulbs. That is plenty of light for hairgrass, and based on the charts in the manual, the light would be adequately uniform over the whole substrate." This means, with all 4 bulbs on, and the light 33 inches from the substrate, you get about 70 micromols of PAR, which is plenty of light for hairgrass. If you want to use only two bulbs, you can lower the light to 23-24 inches from the substrate and get 45-50 micromols of PAR, which is still very likely to be enough light for hairgrass. If you don't mind using all 4 bulbs for the whole photoperiod, just leave it at 33 inches and run all 4 bulbs for the whole photoperiod for 70 micromols of PAR.