There have been at least 6 versions of the AMS Bottom Cover Unit, each with variations on the number and size of vertical wall cavities. Because of this, it's been difficult for both modelers and makers to get the right fit. 

While discussing remix options with @bedebe, I decided to try to solve that issue. I've also provided options for an integrated build plate holder and side brace, with or without x6 Gridfinity bases and/or braces. 

While discussing additional options with @AJarrett46, we came up with the middle brace for the third tier, the wide bracket and brace options for added stability (without requiring additional 2020 Aluminum Profiles), and I modified the braces and brackets to resemble 2020 profiles.

Updates:

• 26-OCT: New print profile! All braces and brackets shaped like 2020 profiles - optional full-width top bracket and center brace
• 05-OCT: For Front-Facing profile (1) removed inner bevel from all channels and increased the depth to 25mm 
• 02-OCT: There are now 3 print profiles to choose from based on the placement of the screws
  • Front-Facing Screws: Places screws in the front and back of all braces and brackets
  • Mostly Side-Facing: Places screws on the side of braces, and brackets that don't have obstructions (all except 03, 05, 07, 09)
  • Brace-Only Screws: Places screws only on the side of the braces (02, 04, 06, 08, 10, 14), and the center bracket (18), and requires fewer screws 
• 29-SEP: New 3-Tier option for 3 vertically stacked AMS!
• 28-APR: Added options for 80 & 160 filament swatches
• 19-APR: Added options for Gridfinity plates

A complete set includes:

• For 2-Tiers:
  • 2 x Upper Brackets
  • 2 x Side Braces
  • 2 x Lower Brackets
  • Optional Gridfinity and/or Filament Swatches
• For the 3rd tier add:
  • 2 x Middle Brackets
  • 2 x Side Braces

Combinations include (but are not limited to):

1. For 2-Tiers: (if using print profile 1, optionally replace 01 with 20 + 20 for full-width bracket - and add 6 screws without nuts)
   1. 01 + 02 + 02 = Frame-only (8 screws + 8 nuts) 
   2. 01 + 02 + 03 + 04 = Small Plate holder on the left  (12 screws + 12 nuts)
   3. 01 + 02 + 05 + 06 = Small Plate holder on the right (12 screws + 12 nuts)
   4. 01 + 03 + 04 + 05 + 06 = Small Plate holder on the left AND right (12 screws + 12 nuts)
   5. 01 + 02 + 07 + 08 = Large Plate holder on the left (12 screws + 12 nuts)
   6. 01 + 02 + 09 + 10 = Large Plate holder on the right (12 screws + 12 nuts)
   7. 01 + 07 + 08 + 09 + 10 = Large Plate holder on the left AND right (12 screws + 12 nuts)
2. For 3-Tiers add 18 to any of the options above (if using print profile 1, optionally replace 18 with 19 + 19 for full-width brace)
   (8 screws + 8 nuts - and add 6 screws for the wide brace)

Optional Gridfinity and Filament Swatch add-ons:

• 11 = 1x6 Gridfinity Brace on left, compatible with combination B, D, E and G 
• 12 = 1x6 Gridfinity Brace on right, compatible with combination C, D, F and G
• 13 = Connectors and 1x6 Gridfinity Base on left and/or right, compatible with combination B, C, D, E, F and G
• Optional magnet covers for a clean look, or to keep loose magnets from coming out
• 14 = 80 Filament Swatch Brace on the left, compatible with combination B and D
• 15 = 80 Filament Swatch Brace on the right, compatible with combination C and D
• 16 = 160 Filament Swatch Brace on the left, compatible with combination E and G
• 17 = 160 Filament Swatch Brace on the right, compatible with combination F and G
• If using print profile 1: add 2 screws + 2 nuts to control height for 11-12 and 14-17

In addition to the printed parts, you will need the following:

• For 2-Tiers:
  • 4 x 400mm (or 420mm for full lid clearance) 2020 aluminum profile
  • M5x12mm Countersunk Hex Socket screw & M5 T-Nut based on selected options (counts provided in red above)
  • For added stability, use the following optional parts
    • 2 x 380mm 2020 aluminum profile
    • 4 x 6mm L-Joint Brackets and screws
    • These are not necessary if using optional wide bracket 20 from print profile 1  
• For 3-Tiers add:
  • 4 x 380mm (or 400mm for full lid clearance) 2020 aluminum profile - the top tier uses 20mm shorter aluminum profiles.
  • M5x12mm Countersunk Hex Socket screw & M5 T-Nut based on selected options (counts provided in red above)
  • For added stability, add the following additional parts:
    • 2 x 380mm 2020 aluminum profile (in addition to the ones for 2-Tiers, for a total of 4)
    • 4 x 6mm L-Joint Brackets and screws (in addition to the ones for 2-Tiers, for a total of 8)
    • These are not necessary if using optional wide brace 19 from print profile 1

For Gridfinity base/brace plate options:

• 12 or 24 x 6x2mm neodymium magnets each for 11, 12, or 13 - 2 for opposite corners or 4 for each corner per grid