Grub2 dual boot with Ubuntu or Mint 18 on encrypted disk

I am trying to add remix OS as a 2nd boot option to a machine that is currently single booting Mint 18 with full disk encryption.

I followed the tutorial for the new marshmallow Remix installed alongside Mint and it worked great on a non-encrypted test box, but I'm having issues doing it on my primary laptop that was installed with full disk encryption option at install time for Mint 18.

How do I need to modify the grub entry for Remix to make it work? For reference here is the grub setup for my Mint installation:

Code:

---

menuentry 'Linux Mint 18 Cinnamon 64-bit, with Linux 4.4.0-21-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-4.4.0-21-generic-advanced-1e6da0b0-6645-4904-a8f7-0c2e7ddbce83' {
                recordfail
                load_video
                gfxmode $linux_gfx_mode
                insmod gzio
                if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
                insmod part_msdos
                insmod ext2
                set root='hd1,msdos1'
                if [ x$feature_platform_search_hint = xy ]; then
                  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,msdos1 --hint-efi=hd1,msdos1 --hint-baremetal=ahci1,msdos1  ffd7222b-aa1e-44d6-a010-e33cefd386d1
                else
                  search --no-floppy --fs-uuid --set=root ffd7222b-aa1e-44d6-a010-e33cefd386d1
                fi
                echo    'Loading Linux 4.4.0-21-generic ...'
                linux  /vmlinuz-4.4.0-21-generic root=/dev/mapper/mint--vg-root ro  quiet splash $vt_handoff
                echo    'Loading initial ramdisk ...'
                initrd  /initrd.img-4.4.0-21-generic
        }

---

Here is the default Remix OS entry that I need to modify so that the encrypted volume is mounted first the same way it is for Mint. I have no idea what I need to do to achieve this. Looking above I see the set root options many times... evidently that doesn't do what I thought it did because I've tried every version of setting the root below and getting it badly wrong. My remix lives in /remix just like in the tutorial except that my / is on the encrypted volume.

Code:

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menuentry 'Remix OS' --class android-x86 {
        insmod part_gpt
        search --file --no-floppy --set=root /remix/system.img
        linux /remix/kernel root=/dev/ram0 androidboot.hardware=remix_x86_64 androidboot.selinux=permissive CMDLINE
        initrd /remix/initrd.img
}

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