Multiple EF -> E mount adapters (with electronics) I tried (Commlite and Viltrox) turned out to be unusable (or only barely usable after severe, warranty voiding modifications) due to them being 0.3-0.5mm short of the proper flange distance. This is fine or even desirable with unit-focusing primes, but leads to severe image quality problems with internal-focusing zooms and wide angles (which work fine on an actual EOS. Eg Sigma 8-16, which shows brutal spherical aberration with the flange distance even 0.1mm off).
Which of the adapters that are or have been available will offer the same tight tolerances as an actual EOS camera in that regard (and offer at least electronic aperture control)? Is Sigma's costly MC11 adapter accurate?
(Aware that this might or might not be considered a shopping question... however, criteria are not exactly subjective here).