[masraum]

Wouldn't this be less about area and more about circumference. ie, circumference of a circle of 2" diameter is 6.28" If you had an oval with a long side of 2.5" what would a 6.28" circumference make the short side length be.

For a VERY rough approximation (without having to look up the formula for an ellipse), you could probably use a rectangle. Since it's not actually a rectangle, but an oval, the dimension would be slightly higher.

2.5x2 + Xx2 = 6.28.

x = ~.75

It does seem like vacuuming would be better. I've had a couple of leaf blowers similar to what's in the picture, and they usually have the vacuum attachment that mounts to the bottom with a bag that goes where the usual nozzle is.