[rcheshire (Rowland)]

Here's an old 1000D sensor with frame and PCB (including metal shield) Identical in construction to the 450D, except fpr the megapixels, of course.

The gap is 1.3mm. The tongue of the cold finger is nominally 43 x 27mm to cover the sensor back completely while not touching the sensor pins. The sensor pins must be insulated from the edge of the copper. I use thin plastic strips 45 x 2mm inserted either side of the cold finger. They slide into place alongside the row of pins.