never built this model, sorry nor have I ever seen one, but it was one undeveloped to full that John Wright inherited when he bought the company from Frank Hinchliffe.
Now, although frank was a fantastic modeller he didn't suffer fools ( the buying public as a whole)gladly and his development was at times hit and miss, expecting the Jo public to sort out the problems themselves.........after all, he would say...........!"I'm not selling airfix kits", and so some of the parts of his kits didn't fit as they should.........and this part is probably one of those parts.
Presuming the sheer line of the deck that you have marked out is correct, then you have done absolutely nothing wrong, and it's just a bodge on the part, but you will only be able to ascertain that once you have marked the sheer line on the inside of the hull for the correct line of the deck.
neil