Which instrument is the most important?
I felt that I wanted to see the tacho, so I just swapped the speedo and tacho aross, now I can only see what speeds I'm doing up to 70, after that my hand obscures it, using the 11.5" Motolita, but if the tacho is showing 4k then I know I am in excess of 80. The down side is that you can't always see if the indicators are flashing and as they are a bit hit and miss, this is important. It also obscures the voltmeter readout!