I've just discovered this morning that the response is different if inches is selected as the units, maybe it's a 25.4 factor I don't know yet but the zoom and viewscale are affected by it.
There is an enumeration for units; (the incorrect (for me) spelling of metre is killing me

)
Millimeters= 0, inches=1, Centimeters=2, Meters = 3,Thousandths = 4,Unknown = -1
I found that even if you change the language, text in the enumeration remains the same, that is what you would expect I suppose, but you never know without testing.
On my system, when I zoom in so that vp.ViewScale = 500, I get a measure of about 3.1 units across the screen width.
Because I'm using vp.ViewScale in a simple non linear equation for pan speed, movement was different for different units, it was a 25.4 thing.
For anyone interested the values for vp.ViewScale when CamBam starts (on my PC at least) are;
mm 3.779
inches 96
cm 37.79
m 3779
thou 0.096
unknown 3.779
So I applied scaling factors so my base unit for pan speed when CamBam starts is;
3.77 for all units.
New update added, this now compensates for selected units.
Edit: And then I saw these in CamBam 'Options'
Field of view 90
select fade 50
view focal length scale 2
view projection mode Orthographic

maybe I need to play with these too
Edit: Old version removed please see further down thread for latest version.