I have a Freestyle Pro ergonomic split keyboard, which unfortunately does not include palm rests or support tenting out-of-the-box. There is a kit you can buy called the VIP Pro that provides palm rests and adjustable tenting. I wanted those features, but not the cost of the added kit, so I designed my own solution. This is the product of that effort. My design loosely copies the look of the VIP Pro palm rest, but I came up with my own solution for adjustable tenting. Like the VIP Pro kit, this kit does require the use of the palm rests in order to use the tenting feature, but the palm rests can be used alone if you don't want/need tenting.

Minimum Required Parts
If you just want the palm rests, you need to print:

• 1x palm-rest
• 1x palm-rest (mirrored - you have to mirror it yourself which you can do in your slicer)

In order to build a full tenting setup, you'll also need at least:

• 2x tent-kit-lifter-rail
• 4x tent-kit-foot
• 2x M3x4mm threaded heat-set inserts
• 2x M3x4mm bolts (I used socket heads, but any head type should work)

This basic setup will give you around 5 degrees of tent. You can increase this by adding as many pieces of tent-kit-spacer (two lengths are provided) as it takes to get the desired height/angle. My needs are met by the minimum configuration and I haven't tested out how high it can get before the design becomes unworkable, but I estimate that you can easily get to around 30 degrees of tenting with this system, which is where the VIP Pro kit also tops out.

Assembly
Install one heat set insert in the hole in the bottom of each palm-rest part (if using the tenting kit). The palm rest clips onto the front of the keyboard by lining up the tabs in the V-shaped groove with the slots on the front edge of the keyboard and pushing firmly into place. This should be a fairly secure fit, with clips on the bottom of the palm rest latching onto matching catches on the bottom of the keyboard. The tent-kit-lifter-rail part slots into rectangular holes on the bottom of the keyboard, and then screws into a threaded insert in the palm rest using an M3x4mm screw. The tent-kit-spacer and/or tent-kit-foot parts thread into the large holes in the tent-kit-lifter-rail. The tent-kit-spacer parts thread into each other so you can stack them to the desired tent height.

Additional Notes
 

• I have included STEP files for each of the parts to make them easier to modify or remix
• Since the top surface of the palm rests is curved you will get some banding, but with light sanding this hasn't been an issue for me at all. If the raw plastic is too uncomfortable for your palms, you can get some self-adhesive closed cell foam, cut it to shape, and stick it onto the palm rests (I haven't needed to do this, but I bet it would be comfortable and might give a more quality look and feel)
• All models are in the orientation I designed them to print in, and I've modeled in the supports where needed so make sure you turn support off in your slicer. If you've got a decently tuned printer you shouldn't have any trouble removing the support pieces; for me they snap out easily with a satisfying click and leave nice clean surfaces, and I'm just using a cheap bedslinger. The modeled supports are designed for a 0.2mm layer height. You could maybe get away with smaller layer heights with a little less overhang quality, but going with thicker layers will risk the supports fusing with the part and being difficult or impossible to remove
• Hopefully it's obvious which parts are support pieces that need to be snapped off after printing. If not,  let me know in the comments!
• The V-shaped slot that seats onto the front of the keyboard has a fairly steep overhang (~70 degrees). It prints like a champ for me, but you may need to add supports in your slicer if your printer's overhang game is weak
• PLA works great for everything if you want, but I recommend printing the feet in a flexible material if you can (especially if you have one that gives a bit of friction like Varioshore or TPU Air at higher temps).