I've been debating back and forth about the best way to attach the angle iron for my V-groove wheels to the top of the rail. I'd originally planned to do it as shown on the left, which would require a lot of drilling and countersinking, etc. over about 140 feet of railing (2x 70 feet). What I realized though is that doing so eliminates any possibility of controlling the height of the rail, and if the screw goes in wrong, then the rail is being supported on the screw rather than flush on the wood base, which would most likely shear the screw (or bend it if I'm lucky) as the roof rolls over it.
Instead what I'm considering is what's shown on the right hand side of the picture. No countersinking would be required, and simple notches with an angle grinder would be enough to keep the rail from moving. I'd also have some level of vertical control for shimming or other adjustments to the rail.
So what have others done on their rails?
On a related note, what do people typically do for joining the segments of angle iron? I know I could weld and grind them, but that adds the possibility of warping, but more importantly adds the risk of burning down the observatory frame I just got built! That's something I'd rather avoid...