You should be able to turn out some nice buds with your setup. I really like the 2 chamber design, And as long as your not having any problems with heat add as much light as your can. For the size of your bigger chamber, 2 of the 125w bulbs will work great, as you saw that is exactly what I have. I may add a third light to my setup after the summer, but it gets real hot where I live and I don't know if adding more heat load to my cabinet is a good idea. I had no problem with my veg under the 2 lights and even though my bloom stage is going great I bet I would get more yield with a third bulb. With the sockets I used you just need two holes to mount the socket and then just bend the strap steel in whatever shape you need to get it mounted and you will be good to go. Thanks for sharing you design, I love to see what other people are doing.
Hasta,
Jack