Why don't you do it the other way round by using the following approach:
1.) Prepare a Backup Drive which you format with HFS+ [(Mac OS Extended (Journaled)] and a GUID partition table by means of
Apple's Disk Utility. This will create an empty HFS+ Partition and a yet empty EFI-partition on your Backup Drive.
2.) Clone your HFS+ System Disk to the HFS+ Backup Drive with Carbon Copy Cloner.
3.) Copy the EFI-Folder on your HFS+ System Drive to the yet empty EFI Partition on your HFS+ Backup Drive. Now you should
have a valid and bootable HFS+ Backup Drive of your HFS+ System Disk.
4.) Verify that your HFS+ Backup Drive boots and works properly.
5.) If everything works fine convert the former HFS+ System Disk to APFS by using the following approach:
a.) To know the exact path of your HFS+ System Disk you want to convert to APFS (<disk>), run the the following terminal
b.) To convert <disk> into APFS run the following terminal command:
Code:
diskutil apfs convert <disk>
c.) Before booting your APFS System Disk, verify that you have the proper apfs.efi in /EFI/Clover/drivers64UEFI/.
I guess that's all!
Cheers,
KGP