spring loaded clips don't push contacts against each other so as long you insert plug all the way in it will work as well as with the clips.
at the end of the day it is much cheaper to replace charger than n900 itself especially when you imported your unit like some of us did and with nokia not having international warranty as far i know i feel happy about grinding down few plugs and if you want to sell your n900 one day in its orginal condition just buy 2nd charger from nokia, and 2nd usb cable, they are cheap.
we not doing any modification to n900 itself so at worst if you grind too much of your plug it will only cost you pocket change to get new charger