I have an answer, let me explain.

the usb device in question is the new Tosh 100mb 2.5" drive in a usb caddy (host powered) and is therefore quite small, and carrying this into work on the bike is as easy as fitting it in to my shirt pocket or back jeans pocket, the 700mb cd wont fit as it is almost twice as wide and I could never find a happy medium by sticking it down the back of my undies!!!!
the drive comes with a leatherette pouch which is just big enough to house the drive and an 8cm cd or business card disk.
anyway, it turns out that that ole < 50mb "Damn Small Linux" has been updated enough to work with Knoppix' new (3.4) boot procedures, so using dsl-0.8.4.iso
Code:
dsl fromhd=/dev/sda1 home=/dev/hda1 myconfig=/dev/sda1
boots the full 3.4 knoppix pmi on my sparkling new drivey toy.
and even doing it the lazy way -
Code:
dsl home=scan
and then ejecting the cd after miniroot loads actually works.

now to buy and test those 8cm dvds to slip down the other side of the pouch.
hopes this helps anyone just as anal, and thanks to all interested readers.