As its been said, scaling is not difficult. Start with what you know. As an avid scratchbuilder, I HIGHLY recomend you start with a virtual grid. You can get one out of most drawing software.
1) Cut and paste what things you do know (even if it's a destroid)
2) Make your calcualtions (eyeball it) by dragging out your Oberth.
3) Give your grid panels a size value to convert it to your model size
4) Take the time and DRAW it (trace what you can)out in the views you can't find
5) Make sure it ALL fits together afterward, paper is cheaper than plastic
Then work your way with points of referance. I am building a 1/200th scale Daedalus and ALL of the measurements listed were WRONG!!! There are drawings that clearly show destroids side by side and other details that make it MUCH smaller than what others say. If you can only verify a missle size, put it on the grid and scale it! I built the "Tunny VTOL" solely by the views and size of a standard size airline door! That was before I got my "Macross Pefect Memory Book" only to find all of the beautiful views and details I didn't have before. Guess what, I was on the mark! The key is spending a lot of time on your PC or paper.