Just got the Ram mount in for my Garmin Nuvi 760 - tested the accuracy of my C90 speedo yesterday... here is what it looks like:
This mount will adjust / tilt in various directions (you don't have to have it "upright" like the way it is pictured)... I mounted it on the bars between the risers.
The speed indicated on my C90 was @ only 5 miles off between 45 - 75 indicated...
Here's a small charting of what I found:
at 76 mph indicated, I was actually doing 70 mph...
75 mph indicated = 69 mph actual
70 mph indicated = 65 mph actual
65 mph indicated = 60 mph actual
60 mph indicated = 55 mph actual
55 mph indicated = 50 mph actual
50 mph indicated = 46 mph actual
45 mph indicated = 41 mph actual
40 mph indicated = 36 mph actual
35 mph indicated = 32 mph actual