I use Hypam at 1+4 and only need to Fix MGIV RC for 30sec
I then wash under running water for 90 to 120sec
I need glass to support my 120 Negs in the Carrier to keep them flat enough during an enlargement - I found they have a tendency to sag from the heat of the lamp - but this is very much dependant upon your particular enlarger set up.
I also had troubled with Newtons’ Rings if I didn't use AN glass - but sadly would often not spot the Newtons’ Rings on the print until after I had produced the print.
The problems with Newtons’ Rings would vary with the weather, warm & dry seemed OK but cool/cold and wet and I was in trouble.
However, I did find trying to keep 4 glass surfaces clean, dry and dust free a major pain in the behind.
Good luck and have fun