Mask Sizing Question

[golfgame]

Having been on Bipap for three months I have tried 4 masks to date. Most recently the Dr office sent me home with a Resproniocs Wisp and an Airfit N-20. Both have a size Lg cushion.  I came across a sizing cutout for sizing that comes with the AirFit.  You align the guide under the nose and it should align with the edge of your eyes. Even tho the guide is listed as being "for Her" it tells me that I should have a small cushion.  It would seem to me that his or her would not matter.
 
Is a guide such as this reliable?  I had been using a nasal pillow prior and find this to be more comfortable. I am just trying to get a better seal. 

What is an acceptable leak rate?