There is, AFAIK, no problem UNIONFS-mounting the cloop Knoppix image with an unused instance (copy) of knoppix-data.img read-only. That is a safe way of handling remastering. "Remounting": If a second ro-mounting of an already mounted (rw) image is meant, I can't really see the good reason for it. Not very safe IMHO.
$8.50
Knoppix Live GNU Linux System 9.1 on Bootable CD / DVD / USB Flash Drive
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KNOPPIX 9.1 LINUX INSTALL & LIVE DVD
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Knoppix Linux Bootable OS v8.6 "Original Live Operating System" 16G USB Stick
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Knoppix 9.1 Live Linux GNU Bootable USB Flash Drive USA
$19.99
Linux Knoppix 4.0.2 Installation Disc
$39.99
Acer Aspire One 9 inch Netbook ZG5 512MB RAM 8GB SSD HD Knoppix Linux WiFi VGA
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$8.50
Knoppix 3.4 Linux installation CD
$14.00
Knoppix Linux Bootable OS v8.6 "Original Live Operating System" 32G USB Stick
$20.30