[jyl]

The inside of your squarish oval will have a wide dimension (call it width) and a narrow dimension (call it height). They are dependent on each other, if you squeeze it to a narrow slit, the width dimension will approach 3.15" when the height approaches zero.

Easiest thing to do it try it.

Next easiest is to wrap string around the end of your blower tube, measure length of string, if it is less than 6.3" then the 2" i.d. PVC tube is big enough.