Just a simple top rail for the Stryfe. It slides on, snug, and has some very mild tabs to lock into place. It doesn't require any hardware to stay in place (in fact, it's not easy to get off). It's easiest to get on with the jam door open.
I don't care for the gap under the front end, but this model was designed to be the bare minimum rail. The intention is that it will be part of a remix or two that extends the rail beyond the jam door.
I printed it upright on the front end with supports. I made the mistake of printing the first one with the picatinny side down and it was impossible to cleanly clear the supports out of the inner grooves. If you have water-soluble supports, that's probably a non-issue.
I didn't need any for the slide, but some of the picatinny grooves cooled a little over spec, so they needed to be opened up a little. Two minutes work, tops.