I'm not sure if a 4-quart pan is actually any shallower... with the oil pump pickup being located in the same spot on both pans (gotta be close to the lowest point, don't ya think?), I think the 5-quart pan is just wider at the bottom. But it might not actually stick down any more than the 4-quart (or there may be a slight difference, but likely not much.)
The reduced oil capacity will also make your oil temps run higher.
That said, to make a 4-quart work on a turbo diesel, you'd have to drill a hole into the side and add an oil return fitting of some sort, like is on the TD pan.