Polygonal Viewports

I recently had one of about 8 layouts in a drawing which was slow to print and made PDF's of about 25Mb while all the others were ~300k.

That vport is a roughly triangular polygon shape in the top left half of the sheet border.

When I double click to get out of M:layout, it has to be outside the border because the triangle is seen or acts as an imaginary rectangle.

I dragged the triangle into roughly a full rectangle and deleted the unwanted detail (there wasn't much), then printing it came back into line with all the other vports.

Has anyone else noticed this behaviour?

It seems from this that odd shaped vports are possible, but it's best to go for rectangular.