Thats one of the pit falls of 20 year old anime and SciFi. nobody ever kept accurate drawings and plans back then (with the exception of a certain Californian based film producer), nowadays its part of the process. You know that there will be countless companies wanting action figure rights, and model companies wanting to build the ships and vehicles etc. Macross was not alone I Recall several instances of size changing in TF`s Bumblebee was always changing scale.
In the real world, modeling and toys you'll never have this problem as there are examples of the real items and nowadays cad drawings to build from, plus the Manufactures will sue if you don't get the representation of their product right.