I had a lot of problems with drawings not fitting and edges missing. I figured out that it was the margins. With the HP 430, not only is there a margin, but also a tolerance. If you don't add the tolerance to the margin, then your plotter may not print the entire drawing.
I created a drawing template that has little boxes in the corners that are exactly the right size to account for the margins and tolerances. When I plot full size, I use plot window and endpoint snap to pick the corners of those boxes. This fits perfectly on the HP430 (36” wide) plotter and does not waste any paper.
When I plot half size, I plot window the entire thing, including the dashed trim line. I still plot with the paper size set to 24 x 36 and with the “inked area” setting on. This effectively allows me to cut the margins in half.
Here is a copy of the border sheet that I use.
http://delapp.com/cad/24x36-border.dwg
There is also a small line on in the upper left corner of the drawing. Using the plotter's “Inked area” setting, this adds a small inked area there and shifts the plot to the right creating a binding area on the left side of the drawing.
Mars