The question can arise as to how the seal can be aligned neatly and secured so that it does its job. This was the technique I used to obtain a seal that does not leak, but it does require quite a bit of flexibility -- or the help of someone who has it. It is best done with the fuel tank out of the car (and perhaps the battery) and someone on the outside to close and open the boot lid.
Lay the seal on the flange of the shroud all the way around, with the ends of the seal butted at the bottom and the flat side of the seal toward the boot lid. Secure it to the shroud at intervals around its length with masking tape.
Get into the boot with a light and a pencil. Making sure the seal fits properly on the shroud flange and mates well with the boot lid around its entire length, mark the inside edge of the seal on the bottom of the boot lid.
Now you can get out of the boot, remove the masking tape, and glue the seal to the boot lid with contact cement or weatherstrip adhesive, following the pencil mark and starting at one end of the seal. Do not stretch the seal as you work you way around the boot opening.