I notice that in your layout you have defined some FOUR_LEVEL mappings. I am curious since for me, the only FOUR_LEVEL mappings that work are those of 3rd level chars who have an uppercase counterpart. But your layout, as well as another I have seen from a French user show that functional FOUR_LEVEL layouts are possible... but I fail to find what is the "magic" is to make them work on my N900.

By the way, I think you could have implemented your layout say within the US section... instead of modifying the "english-base" which affects all other layouts that do a default include of that base.

--denis