This model allows for a 1s 450mah battery to friction fit into the 2s Mobula8 battery tray while tucking an XT 30 addapter underslung within the original Mobula8 battery tray. I have tested 1s to work well for indoor flight using Mobula8 HD with HDZero VTX attached to vbat (DJI plug). I expect the Mobula8 Analog and Walksnail Avatar HD Mini 1s versions will function on 1s. Sorry DJI users, I expect you will need to stick to 2s.
Use OpenSCAD to reder the .scad file and export to STL for your slicer.
I printed in TPU with 15% infill and no supports.
I was a little tempted to add a positive retention system to clip into the lower supports of Mobula 8 battery tray but so far I have not found that to be needed.