Haha, we've all been here before. That first effort, what a great feeling it is too!
I would definitely mount those bulbs sideways. my first grow I didn't, and during the second I did, seems much better for the plant, especially if you try to keep the canopy even with some LST.
I decided to grow just 1 plant in my 40cmx40cm box, using 6 bulbs: 3*23w 6500,1*18w 6500,2x23 2700k
I have 2 boxes the same size and will use one box with 18/6 the other 24/0 using the same bulbs, same nutrients.
Here are some updated pics of the growbox, temperatures, i planted a seed tonight