@DoubleD Currently living the saying, "If you need something done right, do it yourself." If you recall my A/C story, I'm multiple hours into cleaning and re-insulating an A/C wall sleeve, padded in every corner (except where the water leaks) for maximum vibration reduction. Time is just flying. DIY living is the true and correct male experience.
@DoubleD just a follow-up. The A/C is now 90% quieter, as far as the rumbling of its inner workings is concerned. I think making sure the thing is squeezed in (with foam tape/soft insulation) from at least two sides, like a clamp, preventing it from shaking, is the cure to its noisy degeneracy. The more you know.