Found this whilst surfing the net.

http://growagoodlife.com/build...

that will work

What I really like about that is the idea of putting the two 23" shelves side by side -- it's not that easy to find shelves that are wide enough for the 4' lights! My setup is a heavy-duty shelving system that is wide enough, and also deep enough to allow 2 lights for each shelf. But putting the two smaller units together would really be more manageable -- and probably less expensive!

I have the exact shelf system shown in the link above so I may just do this setup.

I also found an interesting link on balanced cfl lighting which intrigues me.

https://m.youtube.com/watch?v=...

Price seemed very reasonable for that set-up. Best price I found on 4' shelves (heavy duty, 5 adjustable shelves) was about $90. This seems like a great alternative for a lower cost.

I've actually got one of those shelves shown in the picture in the article .. they are a nightmare to put together - on the other hand, the system is easily adaptable to other types of shelves.

I have three different shelving units, one in the garage that is similar though more heavy-duty than what's shown. Those shelves are 4' W, 6' H, and 2' deep. I have three units and each unit will hold many hundreds pounds of weight. In one greenhouse, I use shelving that came with the greenhouse, and it is also very heavy-duty construction. Those shelves are 12' W and 2' deep on the bottom and middle shelves and 12" deep on the top shelf. The third shelving was purchased from Lowe's, and all these are 10' W and 2' deep on the bottom and middle shelves and 12" deep on the third (top) shelf. I used the 12" deep shelves to afford more light onto that bottom and middle shelves. They are lighter duty than the other two shelving units but were much less expensive.

The heavy-duty shelving will last a life-time and the Lowe's shelving, since it is in constant dampness, will probably last 10 years, as long as I re-paint it every 2-3 years to keep rust at bay.