Lower mounting bracket to locate a MegaSquirt MS3 ECU in an 01-05 Miata (this may work on a 1999-2000 NB1 however I don't have one to test.)
Two versions, one without a hole for a bolt of ziptie to secure the ECU (0105MiataMS3Mount.stl), one with a bolt hole and ziptie provision (0105MiataMS3MountHole.stl).
Remixed from Risi_turbo's design on Thingiverse here: https://www.thingiverse.com/thing:3849892
Changes:
Thickened most parts
Radiused corners to provide better load distribution
Added support behind the cradle where it comes off the main structure
Added bolt hole and ziptie provisions
Notes:
Print with 3-4 walls depending on nozzle size.
30%+ infill recommended.
The author hasn't provided the model origin yet.