It seems like much of the correct forum selection problem stems from topics that cross over into different categories, and if we could tag multiple categories, some of that would be alleviated.
Would it be possible to place a certain post in multiple forums? For example, if I had an electrical question about a 3-rail traditional toy train, could I tag it in multiple forums - both the Electrical and the 3R TTT forum? Or posting whether a certain 3RS model accurately depicts its 1:1 prototype, it may be useful to appear in the 3RS and the real trains category to get experts from both sides.
Technically, it might be easy or very difficult to pull off - I don't know. Any thoughts?