Hello J L, you might be interested about another method to get plans for building models which I have used many times for years.
When searching something to build for next project, I am searching from internet, for example blueprints (
https://www.the-blueprints.com/search/Mercer/ ), if I could find there the item I am interested of. This time the famous racing car Mercer Raceabout. The file could be of any format, .jpg, .png, etc.
Then I am printing this on paper in whatever size it will print. After that a little calculation.
For example I know that the wheelbase of real Mercer was 108". This equals 2743 millimetres. I want to build the model in 1/6 scale. So the wheelbase of the model must be 2743 mm divided by 6, which means appr. 457 mm.
The car wheelbase which was printed on paper is 275 mm. To get it in the scale I want, it must be enlarged by factor 457/275 which equals appr. 1.66.
Now I go to a photocopying company with my printed drawing and ask them to enlarge it by 166%. With their big printers it takes about one minute to have the drawing in the size I want. The cost for this was about 6$.
Of course the enlarged drawing has lines wider than they would be when "properly" handled, but when I measure lines "middle to middle" there is not much error.
Below is a picture of the two Mercer drawings. On top is the drawing directly printed from downloaded .jpg file, and below the one enlarged by 166%, which is ready to be used to build the model: