Might I suggest a different approach?
Try running strut horizontally, at about 'knee height,' along the walk (the idea is to make it look like it was a middle rail for the walkway). Attach the conduit to the strut using parallel clamps like these: http://www.mcmaster.com/#strut-channel-straps/=12r82g6
I'd prefer coated conduit (Ocal) for this job; in any event I'd use rigid, with threaded fittings wherever possible. PVC just seems to droop and crack. I'd also go up a size, to 3/4".
Forget "Bell" boxes. This is a place for the cast FS-type boxes.
Fixtures are available that will screw directly to conduit. Again, 3/4 rigid will give the support you need.
Coat ALL threads with anti-seize before final assembly, to keep things from rusting together. T&B's "Kopr-coat" is even UL listed for this use.