[CentOS-virt] kernel-plus PXE virt-install with Xen?

I'm trying to figure out how to replace the vmlinuz and initrd.img from CentOS 7.4 with "fixed" kernel-plus versions in order create CentOS 7.4 VM's. So far I'm stuck booting via 7.3 install, adding new kernel-plus and upgrading to 7.4. I've not found any complete Google answers and was looking for help making sure I choose the correct approach.

I've tried to build an initrd.img from a kernel-plus booting system via "mkinitrd -f -v /boot/initrd.img $(uname -r)", but the file size is less than half the one from CentOS 7.4 (17MB -vs- 47MB). I'm not even sure I can just replace those files yet either.

Any help going the correct path?

Thanks PJ