Measure the plank thickness and buy some strip styrene the same or close to it in thickness.
Chop/cut to the width of the flight deck. Sand the corners slightly to try and match the width of the gap.
Invert the forward section on something impervious to thin cement *just in case* and line each plank up - doing this upside down withh line the planks up flat with the deck.
Lightly tack each to the deck one at a time and once that glue has set and you know it's lined up, raise it off that surface so capillary action won't pull the thin cement through the joint and glue the deck down and hit it with more. Let dry fully.That should fill your deck gap, and you can fill the sides with either more strip or putty, etc.
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Tracy White -
Researcher@Large"Let the evidence guide the research. Do not have a preconceived agenda which will only distort the result."
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Barbara Tuchman