just saw this and you've probably resolved it by now - but i'm blessed with big feet (46

) and have to use a wider board (26cm) to avoid heels and toes catching.
3cm overhang sounds too much, but i'd say a bit of overhang is ok as the boot is usually a bit above the board edge itself so you can still angle the board a lot before any contact in turns (if it look at mine its probably a cm or so - maybe nearly 2 even at the very outside bit of the boot).
try changing the angles as jepoy said - they are marked on the binding disc in case you didn't know!
i use +15 degrees front (ie toes angled towards board front) and -5 degrees on the back (ie toes angled towards tail) -ie slight duck stance and works ok for me. try various and see what feels right and comfortable.
but also make sure binding is set so any overhang is even toe and heel - you can usually put the mounting discs in three or 4 positions widthways to sort this.
good luck!