I don't have a installkernel executable on my machine, yet "make install" has never failed me. "make help" also says it will install to $INSTALL_PATH if no installkernel exists. From the Makefile:
# INSTALL_PATH specifies where to place the updated kernel and system map
# images. Default is /boot, but you can set it to other values
export INSTALL_PATH ?= /boot
So again, it seems "make install" just does the copying for me without the issue of fat finger problems. Unless I'm missing something.