I forgot to take picture of my wiring work before I closed it up.
Here's some picture galore:
playing SMS game and GG game without any noticeable issue. No shrinking like the old RGB mod. The internal LCD has 2 available modes: scanline and no scanline. For the GG game, classic scanline seems better, maybe because I am used to it after 25 years+. But for SMS games, no scanline seems better.
You can change between scan modes anytime by pressing all 3 buttons.
Also my GG has VGA out port and on the monitor I can see quite well if a bit blocky. After looking around my console, I decided port on the side won't work because it's curved and would be a bit tricky to get even cut plus it's also hard to get mounting screws secured near the seam between front and back half. I ended up having it stick out of the back near the converter mounting screw, it just fits if I ever needed a Master Gear converter and VGA display.
The plug does not get in the way of my hands but YMMV.
One thing I noticed, I can't change between internal LCD and VGA on the spot, so I needed to set the dial high for VGA or low for internal LCD. I don't know if this is intended or not.
VGA default mode: (full with scanline)
VGA second mode (full without scanline)
VGA third mode (reduced with scanline)
and last one (reduced no scanline)
It may be just me but the reduced mode looked slightly better with even square pixels while the full screen had a few stretched pixels. This was all on 4:3 display, a 16:9 display (or heaven forbid a monster 21:9 display) that doesn't offer classic 4:3 mode will look awful.
SMS games also looked fine in full screen:
I did not take the other 2 SMS modes, it was tiny. Maybe the tiny mode would be fine if you were playing on a 100" display and didn't like Tetris-esque blocks.
large LCD looks fine with scanline mode. I don't have a working VGA CRT and only got an ancient 15Khz RGB display that is not VGA compatible but I would imagine no scanline mode looks best on CRT due to natural scanlines.
One thing I noticed was that in scanline mode, there were varying brightness level on horizontal lines. I don't know if this is the way the mod was done or if I need to recheck my wiring?
I used an old 15" 4:3 NEC VGA panel that I found at a Goodwill for about $5. It had a full glass front which meant easy to clean. Most LCD has bezel that can trap dust and grimes in the corner.