I've gone down the Boroda hack route on my 350. Worked a treat - all my epubs now display in fontin font.
I did have my 505 as a backup just in case something went wrong, though!
look at this thread for Boroda info:-
particularly at post #14 by Induna - and obviously, make sure you get the 350 software/boroda hack - it ran fine on my windows desktop.
The e-book resder blog CSS method is safer for a start, but the Boroda does work great on a 350....