Waste pipe slope

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I'm replacing a horizontal run of some 3" cast iron pipe that runs near the ceiling of my garage from one wall to the other. The total length is about 225", and the total drop right now is 3.5". This is about 3/16" per foot drop if distributed perfectly. To get up to 1/4" per foot, I would need to open up the wall where the pipe exits and tear out more fittings, etc., so that the pipe can exit the garage about 1 1/4" lower than it does now. This pipe carries all waste for a 3/1.5 apartment above the garage, so one shower, two toilets, two bathroom sinks, and a kitchen sink. They tie in at various points on this horizontal run.

The pipe is old and corroded in some sections, and was hung with plumbers tape only, so the drop is not even - it's flat in some sections and more than 1/4" per foot in others. I'm going to use cleavis hangers on threaded rod from superstrut this time to allow fine adjustments of slope along the run to get it nice and even, and allow future adjustment if the building settles more.

My question is, should I just try to carefully make sure the entire run has an even drop of 3/16" per foot, or is it worth opening up another can of worms by going into the wall so I can get a full 1/4" per foot all the way?
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