Scarecrow,
Do you ever plan to even think about having your plans published?
If you're not using a vector format, you need to have the final version at 1,200 dpi. Which means your working version should be at least 2,400 dpi, preferably 4,800 dpi. Then you can use Photoshop or whatever drawing app you use to shrink the image down to 300 dpi for printing at home or whatever the publisher wants for printing professionally.
I've seen a lot of very crappy *printed* documents that looked absolutely wonderful on my computer. I've even written/drawn some of them.