Vignetting on 6x6 negative with 75mm Beslar 75mm? (Dumb question incoming)

Alright so for years I had a hybrid workflow where I would scan my negatives but finally picked up a darkroom setup. It's a Beseler 23C with a dichro head. I set everything up (power supply, Gralab 645 timer, etc) and figured I would throw in a 6x6 negative to see what it looks like on the baseboard.

There is a Beslar 75mm lens on the enlarger currently and even with the head moved all the way down, here is what I get. What am I doing wrong? From my research, 75mm should be fine for enlarging a 6x6 negative.

Please see attached for image.

Possibly (I'd even say probably) it's the illumination of the negative that is limiting the coverage.
1. If you can lift slightly the top half of the enlarger and peek at the film plane: is the 6x6 area fully covered by the illumination?
2. If answer is no, can you adjust the distance between the bulb and the condenser? Is your condenser (size, number, type, and height of condenser lenses) adequate for 6x6?

I don't have a 23C (67CS); maybe another APUGer can give more specific advice.

I don't have a 23c either, but I believe that enlarger has an adjustable condenser, which is probably set wrong.

The 23Cii I used to have didn't use different mixing boxes with the dichro head. I have never seen one do that, maybe something is misaligned inside tho.

Not enough info included in the original post so some guessing here. 1) You have the Dual Dichroic head. 2) You have the 35mm mixing box installed in the Dual Dichroic head as pictured below. If 1 and 2 are correct you need the larger mixing box.

Any chance someone has tried to put the dichro head on top of the condensors?