I loved Alex English's Cheap DSLR Table Dolly, but wanted to have a longer, single channel on the sled.
Follow the instructions on the original thing, but skip the 2x sled parts in favor of one of these.
I have an (AWFUL) video made while using this. You can find it here:
I printed this on my Replicator at 80% infill with 2 shells in ReplicatorG, and it came out so rigid and tough that I'd trust any camera on it.
My replicator is completely enclosed, so I didn't have any warping, but you might if you're not careful! If you want to enclose your Replicator, take a look at the fantastic: http://www.thingiverse.com/thing:23386. If you want your wide / large Replicator builds to come out well, take a gander at: http://www.thingiverse.com/thing:23257.