Some little hints on working with Plannars (UVW Map Planes);
* Always reset the Scale on a part. (I click it several times just in case, dont ask, I have had it not take a Scale Reset a few times).
* I always click 'Adjust to View' and then I go to the size of the Plannar and punch in the nearest amount in X and Y size, such as 20, 20, or 5, 5. What ever is close. This way, the grid is perfectly square and you will only need to use the 'square' scale tool to align to size.
* You can click 'Fit' which will cause the parameters of the Plannar plane to fit to the part, but you should still then enter the closest size of the X,Y from that point. This just gets it to the closest size first.
When you get proficient at this, you can start doing things like snapping a screenshot of the part at the best angle (doesnt have to be exact left, etc), then pasting it into a layer of your graphics, use magic wand to erase the gray background around the part, save, Alt-Tab back to Gmax, click Material/Reload, click Material Apply to paint the object with the updated graphics, then without touching the angle view, apply your Plannar and adjust the Polygons right to the Plannar mesh in the Mesh Edit window. Voila!
By doing the snapshot right then and applying it to the art, then bouncing back to Gmax and pasting/mapping the graphics right back on it without moving the view angle, you get an elaborate angle 'and' its right on precise, treating the 'view' as a graphics shot.
This enables you to do some painting side by side with model creation and saves valuable time. You can also 'cluster' parts with graphics and later 'attach' them, such as bolts and brake lines to a landing gear leg. This enables huge sub-assemblies to be one massive part, which is possible mainly because they are all mapped to the same graphics sheet.

(Making a engine assembly, having all graphics to be on one sheet, means you can take all the non-Hierarchy required parts and Attach them all together. Then, moving your engine, or hiding it is just a one part job.
You can still map Plannars to sub parts on a massive Attach part, (such as that engine) by going to Element mode, clicking on the part to be mapped or remapped, then adding a Plannar or UVW Unwrap to it to make your adjustments. Then collapse the stack when done.
So much you can do to streamline the build process and mapping...
Bill