This question seems to come up quite often-Why are the original dimensions and the classic era kit dimensions different?  With the cottage kit being the same as the original?

Well, back in the 50 to 60's for sure, the US Post Office had rules governing the size a parcel could be. Thus the kit had to be modified to fit in the box so it could be mailed. We had two methods,

USPS  or Railway Express. For most the the country, that was it and REX was not cheap.

On this I could be wrong, but I don't remember any 48 inch balsa being available until the 70's, so that may have been part of the reason as well. 

The other reason some dimensions don't jive is that in doing wing area, some do only each wing and add them leaving out the fuselage width. Big difference in WA.  As to over all length, some go

from  tip of spinner to bitter end other from cowl ring to bitter end. Again as much as 2 1/2 inches difference in length.  Times and rules change and the "nostalgia" movement brought about Accuracy.....