dont use a hair dryer, you dont need to...
you best off cutting it in half, matching the ends with the side of the bumper.
you need to trim the top of the splitter so they hook round fully, now put a self tapper in the end.
find the centre line of the bumper and trim each piece accordingly.
fix either side of the join from underneath with self tappers then work your way along
(there is a small area on the apex of the bend that does quite line up cuase the radius is different but the rest of the edge is fine)
and bingo!
This is for std bumpers only, abarth and marea bumpers are too round to fit flush.
Rich