OS X running off USB key on EeePC 901

Well, it's not exactly what I was looking for when I started this project, but it's not far off.
Yesterday, it looked like I had come to a very serious barrier but, today, I tried to copy what I already had installed, and optimized according to this guide, on a small and very old external HDD.
This time, however, I wanted to install it to a USB key (HP 8 MB) which would avoid me having to mess up my multiboot system on the netbook and still be very portable (in contrast to the external drive).
I did no more than use SuperDuper (free or unregistered version) to copy from the external drive to the 7.5GB drive on the usb key.
Note that I did this after I had installed Chameleon to the drive.
The copy took about 90 minutes and included, as a last step, the addition of a bootloader. As I had already added Chameleon, I didn't want this but no option was provided to avoid it.
As it turned out, when I tried to boot the EeePC from this key, it wouldn't boot because of a bootloader error.
So, I reinstalled Chameleon and this time it did boot --- but very slowly. In total, the boot to Desktop took more than 10 minutes. This is very much slower than booting from the external drive which took about 2 minutes.
Nevertheless, many things work like ethernet (but my wireless card wasn't picked up), mouse, keyboard, touchpad and browsing.
Unfortunately, Desktop operations are extremely slow, in spite of my recent RAM upgrade, to the point where it's almost unusable.
So, getting it to operate at a reasonable speed has to be my first priority, as otherwise, this will turn out to have been an educational, but pretty useless, exercise.