fuzzy math

Here's the nearly finished quilt top, all for me:I'm going to add a big polka dotted border around it, but am still deciding on the width of it. All of the orange sashing and cornerstones are 3" before being sewn. That's about double the width of the block borders (all cut to 1 3/4"). Using this crude math, I think it'd look pleasing if I make the border double the sashing, or 6". I'm really very pleased with this; selfish quilting is fun! I'm still trying to decide on the backing, and also the quilting. Especially the quilting, and even the thread colour. Normally I quilt in the colour of the sashing, but I'm afraid the orange might be too vivid on the blocks (plus, the orange is really made of magenta and yellow warp and weft).
Here it is again, in the sun on my front yard: