Should I modify the depth buffer size, too?
Yes, do this too.
A 16-bit depth buffer is woefully inadequate. All hardware for the past 15-odd years is absolutely guaranteed to support either 24-bit (with 8 unused), 24-bit (interleaved with 8 for stencil) or 32-bit depth buffers. There's nothing to gain from using 16-bit unless you want to run on an ancient original 3DFX or some weird mobile platform.