[meurglysIII]

I recently bought a Bachmann class 108 dmu (one of the limited edition BR Blue ones from Modelzone). I'm very impressed with it in general, but, whilst the power car is hefty and feels solid, the dummy car is, I feel, excessively light. There's not enough traction to the rails to light the destination boards and interior properly and constantly (The power car, due to its weight, performs very well in this respect). Also, the dummy car skips off the rails when entering facing points off a curve (even when trailing behind the power car).
Trouble is, there's no room in the interior and very little room on the chassis for extra weight to be added. the only possibles are between the battery boxes and on the bogies themselves. Also I'm not that keen on taking it apart just yet! Anyone have any ideas? Is it safe to dismantle?