"high lumen bulbs which are 12 or so inches long"

Those reflectors are not for 12" bulbs. Are they CFL?

Maybe, you can use wing reflectors but it would be cheaper to use different bulbs, maybe, LED BR30 without reflectors, in which case, I recommend these swiveling lamp holders:

http://www.ebay.com/itm/Sigma-Electric-14330WH-Lamp-Holder-White-LOT-OF-2-/311600340586?hash=item488cd3de6a:g:71YAAOSw2GlXH4OG

You can mount these on aluminum angle. but, you will need many more than 4 LED BR30 bulbs.

I was thinking of mounting the bulb and base to a piece of plywood and cutting of the clamping end. Then using chains, lower and raise the plywood over the plants. I don't mind butchering the fixtures, just not sure what the best way to connect them up for this use would be. The bulbs are like these: https://www.1000bulbs.com/category/500-watt-equal-compact-fluorescents-6500k/

Andrew

For this type of bulb, just remember the bulk of the light is generated from the sides not the end. The reflector should extend past the sides of the bulb to ensure best light utilization.

Just google cfl lamp reflector for ideas or add diy when you are handy

https://www.google.nl/search?q=cfl+lamp+reflector&biw=1072&bih=774&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi4gr7e48XPAhVKDsAKHVKtBzIQ_AUIBigB&dpr=1#tbm=isch&q=diy+cfl+lamp+reflector