Build on quarter of it, copy in place, move over, weld. Repeat for the bottom, then soften any hard points in between. The image you have may not be true once scanned and worked up. I'm sure there are other ways, but if its critical to keep the shape, it' how I would Kengineer it.
Start by creating a rectangle, then go to Arrange:Convert to Outlines. Next use the distort tool (on my screen it is the last selection). Then finally use the corner round tool. I am sure there are other ways this is just the way I would do it.
I can bezier the shape and also edit the nodes of a rectangle as well. I was just wondering if there was a way, or a setting in FLexi to do it mathematically so that the top, bottom, left and right sides are equal.
Thanks very much for your input.
Ken Sankey's post pretty much spells it out. Use the existing image as a pattern and create a perfect 1/4 section by equalizing the length and angle of the three nodes that it would take to define the 1/4 shape. Establishing the position of the two end nodes can be done by positioning guidelines at the precise half height and width positions. The end nodes should be on axis and the handles of equal length. the node on the curve should be at 45 or 135 degrees and be a symmetrical node.