It works suprisingly well... in my experience with it, it performs well on punchy bass tracks, but not so well on deep long bassy tracks. But that may be just my experience...
I'd find some anodised screws for the tach and would have drilled the hole for the wiring below the actual tach so it was hidden and looked tidy but overall I like the NASCAR look!
it took ages to find the wiring, but i got the tacho to work by getting the wire through the bulkhead and spliced it onto the light blue and red wire, on the top coil, in the haynes manual it told me that was the engine speed signal wire (and also the negative) it seems to work fine.
The other wires go to the battery, earth and to the ignition.
I didn't put the wires down below the tacho cos there is a huge lump of plastic there...