Vince, did you use a set screw 90 on a straight riser, then just a bent 90 to get it out over the tank? If so, you will definitely want to drill the 90 all the way through, and run a bolt through the fitting, with a nut on the other side and lock washers. It doesn't take a whole lot of strain for the set screw fittings to start loosening up, and I'd hate to see you get everything painted and have you light start sagging towards the left side of the tank. If not a thru-bolt, you could drill a couple smaller holes in the 90 fitting, and then run self tapping screws through the conduit. Or..................get that bender back and do a back-to-back 90 all in one piece of conduit.
Sorry man I don't mean to scare you but just would hate to see that start sagging after a while and having to be messed with after it's painted.