Interesting. Did they say why it was unsuitable to the mission? On paper it is a pure upgrade to the A-20.
I'd love to actually see if there was a physical report that was submitted. In his book Henebry talks about going to the Pentagon to deliver his report on the A-26.
They tested the A-26B and found that the plane did have many positive characteristics, it handled well, had good range, bomb load and engines. The problems they had were somewhat related to the mission profile they were flying.
They felt the cockpit arrangements were inefficient, and pilot visibility was hampered. The engines extended too far forward, he said about to the 3/9 line in the pilots vision. You could only see forward and up, which was a problem when you were making low level attacks in formation. All in all they compiled a list of 32 grievances with the design.
He took the list to 5th Air Force Command and was placed on special assignment by General Kenney to go tell the brass at the Pentagon that they didn't want it and would continue the war with their B-25's and A-20's.