Dog Star
Western Thunderer
This suggestion from Bob is a good candidate - 25th is about twice the width of a 4/0 piercing saw blade so two straight cuts shall do the necessary.I'd go for cut n' shut Graham - it's about saw kerf width so splitting it down the middle and if necessary plating one side over the joint with a small piece of scrap etch....
Why two, other than to get the necessary reduction in width? Consider the queen posts to be numbered 1 to 4 from left to right... if I cut between 1 and 2... and between 3 and 4... then I shall maintain the alignment of the outer queen posts with the solebar and the inner queen posts with the cut-outs of a cross-member (for the truss girders) further along the underframe.
Investigation and success shall wait for the weekend as trackwork is beckoning.
regards, Graham