Yes, please all take care of your back! So precious, safety first. Beyond the weight itself, the way you lift hold & carry stuff is at least as important. You can get serious injury with just a few kg with the wrong set of circumstances. Btw the 5U max size I mentioned above was for a standard model (ie: non-shock mount). Shockmount would make the max acceptable size even smaller + most (especially foam based ones) have some constraints in the way you can safely carry them (position...).