OpenGL share GL_RENDERBUFFER between threads

Dear GameDEV,

Forgive me if this has been answered too many times, I went through about 4 pages of results (here and Google) and none have helped with this question (at least to my current knowledge base)...

I currently have 2 threads (2 contexts) in OpenGL; one to render the frame and one to render all the 2D ontop of the frame (labeled HUD). While this works I can see a significant performance loss rendering the HUD as 1920x1080 vs 1440x810 (witch I know is ~3.5MB difference)

Partial Code:

Renderer:

while((getState()) != STATE_SHUTDOWN) {
	glClearColor(0.0 …