trying to run from SD card

Dear all,
I've been looking at
http://handhelds.org/moin/moin.cgi/HpIpaqH4100Howto#bootfromsd
and I am tempted to try...
I have a french HP4150, a 128Mb SD card, and I'd like to try GPE and/or OPIE.
I guess I could be able to follow the instructions, with only one
partition and testing one or another, changing the startup.txt to
point to the correct /dev/...
My question is very naive: are there any risks? I mean, can I
reasonably assume that trying this Linux will not affect the core
system of my HP? I have basic backups from the device contents, but
not of the system itself. Is it mandatory to do such a backup?
Thanks for any help.
Cheers,

--
Xavier