Hi .Cd
I evaluate VG solution, but I have rejecter it beacose, the back lid isnt' horizontal, but upwards.
look this detail: in the the first, with VG, I think that the flow is like in red arrow
In this below, without the VG, but with the ridge cover, I think that the flow is like:
Because some literatures say the best angle for rear window-beclid is approximately 15 degree, I think the good way it is the last solution.
Dubt rises, with lateral backlid flow that isnt' aligned with the central axis flow (look the fourth image) that, with the central ridge, is more unwaged than the original shape or VG elements.
I think, only best way to eliminate the bubble, it si to add central risge,but I do not want improve one thing and another worsen.
Perhaps, to apply VG in the lateral back lid? or add curves to guide down the outlet air flow?