An update........

I've made sure that the default N64 emulator is libretro. Also, in the Retroarch menu.... the mame overlays/ bezels are clearly downloaded and in the system.

Any advice?

Thx

Whoaaa this looks cool. I feel stupid now, I thought it was a true CRT in your picture! I will definitely try this out now :)

@red2blue, @papinist I think I found something at http://smartretro.co.uk/forums/viewtopic.php?f=3&t=8288

This is the direct link, just in case...
Arcade Bezel overlays (John Merrit)

@meleu yes! weird isn't?

@stinkwinkerton said in Sidebar only overlays?:

@Dochartaigh So, really, it would be cool if we could do an underlay instead of an overlay. Seems a lot simpler don't you think?

You have to remember that overlays are biggest for MAME games I think, and if you remember back to the arcades there were many, well, quite literal "overlays" (over top of the screen) with graphics that overlap parts of the screen themselves (like asteroids, a sword, shield, little monster creatures, etc.). Even old CRT TV's had that little part of trim that commonly went around the edge of the tube (which is why we sometimes see weird stuff on the edges of old console game ROMS - since the very edge of the screen was covered up by plastic moulding way back when).

http://www.arcadeshop.com/pics/donkey-kong-bezel.jpg
http://www.classicarcadegame.rentals/wp-content/uploads/2015/08/Asteroids.png
http://1u88jj3r4db2x4txp44yqfj1.wpengine.netdna-cdn.com/wp-content/uploads/2012/07/donkeykongcrt2.jpg

This also lets them get creative with the "I'm actually looking through dirty plexiglass at the screen just like back in 1981" - which I personally don't get, but whatever.

@johnes
Broadly speaking if you have a Pi3 the mame-2003 emulator is a good bet with the 0.78 romsets.
If you want to stick with the 0.375b then I'd use lr-imame4all - not least because it will allow all the Retroarch functionality as well as easier controller file config.

If you just want to enable a shader (including the one mentioned in the thread you list above), I would strongly recommend using the inbuilt configuration editor:
https://github.com/retropie/retropie-setup/wiki/Configuration-Editor

@Floob pi3 using lr-fceumm.
No overclock.

I think you will be better off asking here:
https://forum.recalbox.com/

I've not really looked at the structure of Recalbox before.

@Floob yeah i realized that. i tried to edit the post before you read it. i guess i was too late. thank you for the reply.