I had the same problem AC53 & the way I solved it was to make short fat wooden wedges (shims)that I could tap in or out all around. This way I got the best possible position for the cab opening & the door shape. I also used some painters tape were the wedges touched the metal. Now the door clears the cowl with just enough room & maybe a hair or two extra but no more.
This worked for me. Hope this can help you.
