Great to see people trying things.
The conduit will induce variances in distance between the two rails because the conduit will not be perfectly straight. It will have a slight bend, or bends, in it, maybe a twist (in appearance). Though PVC pipe is similar to this as well it is not as rigid as the conduit and will "give" some to allow a smooth traverse. A fix for this with the conduit may be paying attention to the irregularities and aligning the two pieces to accomodate them. Some additional cross braces may help as well.
And as for the question in your first post, yes, "ground" is the past tense of "grind." I am a Journeyman Toolmaker and believe I am qualified to make that call.
Hey, I see you are in Cleveland. I am in North Olmsted. You going to the Cleveland Indie Club meeting on the 20th?
Steve