Hi Nov,
Regarding the light spill around your negative carrier; it's fairly common.
I have two Beseler 4x5's with the same problem.
I glued some strips of black velveteen on the lamphouse to act as "curtains" over the offending gaps.
Effective and simple.
If your enlarger is close to a wall, the light spill ...could.. bounce off the wall and cause ...slight... loss of contrast.
Some folks react by paintng the area around the enlarger flat black.
Some even hang black curtains around the enlarger.
I don't like "coal mine" decor, so I eliminate light spill at the source... the lamphouse.
To get some idea of how much light is being spilled and what it's bouncing off of try this:
Cover the lens, turn off the safelights, let yours eyes adapt for a few minutes, and turn on the enlarger.
Can you easily see your easel?
Now, turn off the enlarger and turn on your safelight.
How does the light level on the easel compare?
If the light spilling from the enlarger is the same or stronger than from the safelight... you have a problem.
It's time for the curtains.
Another tip:
Lay a mirror on the easel, cover the lens, and turn on the enlarger.
Study the mirror to discern where light is being bounced down to the easel.
You may need to move those bottles or those developing tanks which are acting as mirrors.
Does the Meopta have a nice shiny chrome column???
Don't worry about silly questions.
The bigger challenge is how to decode the silly answers...
Have fun.
Here's my darkroom:
www.classicBWphoto.com/Darkroom.html
Reinhold