I do a lot of this by hand, see this chart I recently added prop limits to.
You may really like this, it is very useful to know how to do the math for these things and you can find the ruler and grid view functions in a lot of drawing programs or just simply using the copy machine, you make the test print once, comes out wrong, the next one you can get exactly right with WRX.
This is just my favorite kind of stuff, working the numbers, scaling it, looking at it to see if it looks right when done.
When you make your pic a layer, you can move it around to measure it against the scale if need be.
Another favorite technique is in paint shop to take a picture of a component, make it a layer instead of a background, erase away the background ( do this on a raw or large pic, so you can scale down a copy for a drawing you will use it in ), now you can regard this as a piece that you use to test a fit in another picture, like if you are having trouble or wondering how to get servo and radio components in a tough fit or how the engine, scaled, looks on your model, or how a different size of wing or tail or wheels look, etc.
This technique came in handy when working on the Arado 555 ver 1 flying wing, I wanted to see how the components would best fit in this 52 inch one piece 40 size custom aircraft I built, I made layer pieces of the engine top view with prop, erased away the background and saved as a piece to put on the plane ( glo 2stroke pusher ) to see how it would fit, prop clearance at sides, gas tank placement, servo placements inside the wing and the radio. A pic of each piece is saved by itself and just think of it as a piece, then.
