On my convertible, I used double sided foam tape to adhere the GPS antenna center-front of the trunk lid. Right up against the canvas top. The cable was routed :
Along the inside of the trunk lid,
Down the shock/hinge,
Around to the driver side door,
Draped down behind the driver seat,
Up and into the center console.
The Traqmate data unit was velcro'ed in the console on top of "Blue Tack" putty. This putty provides "adjustment" when zero'ing out the X-Y axis. The putty seemed plenty firm enough and recorded measurements were consistent with published magazine numbers (3 seconds average of 1.05 g's on stock runflats). You can pick this wonderful stuff up cheap at any crafts store.
Power is provided right inside the console already.
Separate display was velcro'ed next to the ABS indicator lamp, above the vents and to the right of the vertical guages.