To do this properly you will need to take the bonnet back to bare metal and the area that the bulge is to be fitted with should be sanded rough, 36 grit works well, you need the surface rough if you have any hope of it staying put. the bulge should be trimmed back to just the part you want, usually I'd use double sided tape to attach sheets of 36 grit paper on the bonnet where you want it to go and after trimming the bulge roughly to fit I would slide the bulge back and forth on the paper taped to the bonnet to get as close a fit as possible. then mark the area around the bulge on the bonnet with a marker pen, remove the bulge and paint the area with fiberglass resin, replace the bulge and using 25mm strips of woven glass mat work around the edge blending the tape in, 12mm on the side of the bulge and 12 mm on the bonnet, pays to put something heavy like books on the bulge to hold it down while the resin sets, once it's cured you can just blend it with body filler and refinish the paint. it's not an easy job to do at home but not impossible... takes me back to the 70s and 80s when fibreglass add ons were all the rage
Oh and whether it can be bent by heating or not depends on the resin used in the bulge, styrene resins soften quite a bit with heat and can usually be moved slightly, epoxy resins are far more stable and unlikely to distort.
it's not easy to explain the whole process in a short message so if you want more info PM me and I'll give you my mobile number and talk you through it