Mike, this size is the "twilight zone" for off the shelf framing for me. I try to print only "standard" sizes, so I can buy frames at a store, but 11x14 is a tough one. If you decide to custom mount for size, I would think that a 3" border at top & both sides, then a 3 1/2" or 4" bottom would be just about right. This would place you somewhere around a 17x21frame size, depending on the edge weight of the frame you choose. I've had to change mats on some 11x14 images from white to ivory, just because I couldn't live with a warm tone print in a (relatively) cool mat, just didn't look right to me.
For now, I've come to accept the look of 11x14 in 16x20, but only as a monetary consideration. I don't have time, room, and money to set up the framing area, matt cutter, storage and other areas related to doing a proper frame at home. The alternative of a custom frame by "others" isn't a consideration for me. I have a few custom framed mounts, but only of other people's work, certainly not my own. Best, tim