: Is there a easy way to increase the length of the original
: cockpit without losing it's design shape?

No, but you can come close

A 31.5 x 17 oval is not the same shape as one which is only 30 inches long. If you want to keep the shape then you'll have to increase the width, too. Probably the increase would only be 3/4 of an inch. can you live with that?

If so, space your pattern pieces 1.5 inches apart and tape some extra paper to them to cover the gap. Bend a supple wood strip along the edge of the oval, following as closely as possible the lines of the shape, and run a pencil around this to fill in the missing part of the curve in the gap. Repeat the process for the other side.

Since this is not a very large gap yo might try doing this freehand. If so, after doing bothe sided, fold the pattern in half lengthwise and hold it up to a window or some strong source of light. You should be able to see through the pattern to see if your art work was symetrical.

Good luck.

PGJ