I have several old airfix coaches of the red and cream (Mk 1 ?) variety. Two of them have minor faults. The first has an original, badly moulded corner on the roof that I did not notice when I bought it. The second has a break on one of its bogies that allows one pair of wheels to fall out. Both of these faults could possibly be repaired but, since I have more of these coaches than I need, what I want to do is take the roof of the second and put it on the first to produce one perfect model from the pair. My problem is that I can't see how to dismantle them. I imagine that the roof is held on by some lugs that just snapped in when it was being assembled. However, since I don't know where these are or which way they are arranged, I'm afraid to pull too hard to try to get the roof off. Can anyone help please?