Two Material Extrusion Design Problems

[AcuteAngle 1]

Ok, we have been printing two paste materials with the Ultimaker 2 now for a while, however we are still finding issues with the offset between the two nozzles. To solve this I designed an adapter that allows for two materials to flow out of one nozzle. However, this adapter uses a "door" type valve that closes off one path when the other is printing, and vice versa. This door style valve is so small that I can't print it on conventional printers, as it just comes out as mush. So, does anyone have any ideas as to how to fix this? Or should I just redesign it to allow it to be printable?

And, once this is solved I will still have the problem of adjusting the flowrate of each material individually so that I can push through which ever material I want to without leakage. Is there a way to change the flow rate during each individual layer in the gcode?

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The "axle" of the door valve has a 1.5 mm diameter, and is too small to print with any sort of form.

If anyone can help me improve on the design, I would be very appreciative!