Creating a vignette in Premiere Pro CC 2014

Question

In another thread, I was criticised for the way I chose to create a frame vignette in Premiere Pro.
I've always created a vignette using the circle effect on a transparent video layer, inverting it and applying a feather.  The result can be made fairly subtle if you choose, and the vignette I use the most looks like this (applied over white video so it can be seen easily):
As someone rightly pointed out, the effect isn't GPU accelerated, and with the arrival of Premiere Pro CC 2014, there's a new way to create a vignette using masks, i.e. create a Black Video layer, under Opacity click the ellipse mask, stretch it out to fill the frame, invert it, apply a feather, etc.
The problem is, I cannot find a set of parameters that create a vignette with this new method that approaches the look I am after.  This appears to be mainly because the mask feather is applied to the entire frame and not just to the circle shape of the mask.  That means you end up with a vignette that looks something like this:
Notice the black blobs in each for the four corners.  Also notice that the feathering is being applied to the vignette from the outside of the frame as well as from the inside, i.e. the black blobs are feathered towards the edges of the frame as well as towards the inside.
Of course, you can crank up the feathering to try to remove the blobs, but then the result is that the centre of the frame is now grey:
I've tried using Mask Expansion to push the blobs further out, but the feathering is still applied to the edges of the frame, so you end up with something like this:
Looking closely at the corners (although it doesn't seem to show up very well once saved as JPEG), the vignette goes from white gradually to grey, then starts to head towards white again.
Does anyone think they can find a set of parameters for this new method that recreates a vignette similar to my original?

Answer 1

Those "edge effects" (where "the vignette goes from white gradually to grey, then starts to head towards white again") are caused by the way that Gaussian Blur handles intersections of the mask with the edge of the media.
So "making the mask larger then the frame" (as suggested by Ann Bens) unfortunately won't work because this causes the "edge" to be inside the mask, which is the problem.
But you CAN make the frame larger than the sequence dimensions, and thus avoid these edge effects altogether by using "Motion : Scale" to scale the media (your Black Video Layer) to (say) double the size of your sequence. Now you can create a mask that doesn't hit the edges of the frame, and thus produces no edge effects, and so feathers smoothly all the way out to the edges of your sequence.