i did some testing with my 8 inch fl lens and a 220 mm fl fresnal setup and i get dark corners (8inch lcd the actual lcd will be 5 ich)
when i bring the lens closer to the lcd the corners brighten up but its out of focus
when i use a 13.5 in fl fresnal it gets better but not by much


im thinking if i pull the projector away from the screen farther it will bring the lense closer to the fresnal and should clear up i donno i hope lol

That happened to me when I had the fresnels in the wrong order. U could try switching them and remember that the grooves face the LCD.

i think i got it
i was putting the front fresnal behind the lcd
i moved it to the front and that extra 20 mm -30 mm made all the difference.
thanks