Measuring Airplane w/ existing Tile

Been working for a company for 6 years, ready to do my own thing. Got a job with an airplane shape with existing tile. Whats the best way to measure it accuratly without tearing it out first. I measured the front and side of the cabinets, then measured the back and subtracted the overhang and the 3/8" tile backsplash (to get a rough estimate of what it would be). Plugged everything into my cad program assuming the angles are 22.5s which they should be and the back of the middle piece has a 2" difference (bigger). The other 2 pieces were close to what i had measured through the tile. Not sure if I should use the CAD or go with my rough measurements. Is there a more accurate and easier and cost efficient way? I'm on a budget here, no laser template. Hope someone can understand that, sometimes only I can understand me but it makes sense.