I figured 4 rows 3" apart and 2" to 2.25" spacing in each row. I may also include a few UV LEDs along the centerline. I haven't laid it out yet. I finally received my last supplies including some Berquist adhesive thermal pads. That will be easier then drilling and tapping 160 holes
I have a Hamilton light fixture housing (I think it may have been a MH fixture once) I plan to use to enclose it all and it has a bottom cover with acrylic splash shield