Sorry about belabouring this. If I was able to compile a new kernel (or decide to use the 5.8 kernel) is the only necesary file to copy, the boot image vmlinuz... in the boot folder?
yes all you need is the kernel.
#1. would I be able to copy an install CD onto a hard drive, add the vmlinuz... to the kernel folder and then reburn it, then elect to use that file when booting the installcd?
Yes you can add as many kernels to the kernel folder, as long as they have different names.
you have to add them to the isolinux.cfg file as well.
#2. If I use vinstall-iso under 5.8 how do I get the kernel into the new setup?
I appreciate your help.
You just copy the kernel to /boot and the modules to /lib/modules
I am glad to help