Was having trouble finding the transponder area in my Gravity GT for my TollTag sticker (North TX - Dallas Metro). Originally didn't think it was there. Moved the car outside when it was relatively dark, got a step stool and a flashlight and BOOM! There it was.
Hope this helps. Thanks to all of the other posters who led me here. I've affixed the small TollTag transponder with some blue tape in the area (not pictured). Will come back and post if successful or not.
without flashlight:
View attachment 36978
with flashlight:
View attachment 36977
general placement area bordered:
View attachment 36980
Closer up (zoom in, you can see the grid):
View attachment 36981
Grid from the inside:
View attachment 36976