Yeah, you're going to have that problem. Incidentally that filter was mine, a modified version of another file that was floating around here.

It sounds like you didn't set your dimmer correctly as you should have been able to get a good nighttime match with the one filter. Either that or your printer was set up correctly and didn't throw enough ink on it. Regardless, daytime visibility suffered too much for my liking, and once I started using GPSapp it became intolerable. The problem is simply that the VFD does not have enough light output at that wavelength.(~430nm). That filter is about as good as you are going to get to match VW Blue.

I went to smoke instead.