where to put boot

[larry16110]

I have LLOS 5.8 on a USB external drive.  I want to install 6.6 on the same drive and dual boot both.  I have 4 additional partitions for this, but am getting hung up on where to put the boot files. The installer is not letting me put the files on the partition I created for it.

[larry16110]

Ger are my plans so far:  I made a Timeshift of my 5.8 install.  My 5.8 install is in 4 partitions.  I created 4 partitions for the 6.6 install of which 1 of them was supposed to be the boot partition, but the installer would not let me put it there.  I now plan to overwrite the 5.8 boot partition with the 6.6 boot files.  I will then install the rest of the files on my other newly created partitions thus leaving the rest of the 5.8 files intact so I can access them to transfer to my 6.6 system.  If everything is to my liking, I will delete the older 5.8 partitions.  If not, I can always timeshift back to the 5.8 system.  Any other suggestions appreciated.  thanks