https://www.quora.com/What-is-the-Mach-Principle-What-is-the-experimental-evidence-for-it-What-are-its-implications-on-physics-and-cosmology/answer/Marco-Pereira-1
My position about Mach's Principle is that it is unsupported and refuted by optical and gravitational detection of Neutron Star Collisions.
I identified the only support (Celestial Dynamics within the Solar System requires instantaneous positions to be used in the force calculation) as being the result of using the wrong (empirical Newton's Law of Gravitation) law.
This shouldn't come up as a surprise to anyone since we all know that Newton's Law failed to predict the right Mercury Perihelion Precession Rate.
Of course, nobody can use Einstein's equations for a multi-planet dynamical simulation.
My theory - the Hypergeometrical Universe Theory (HU) provides a trivial replacement for Newtonian Dynamics and Einstein's General Relativity.
In fact, HU fully replaces General and Special Relativity.
IN SUMMARY
To call a theory Machian is a bad thing.