ResMed Ultra Mirage FF Mask Size question

this is my 4th mask. Tried the optilite, the comfortgel nasal, the Hybrid, and now the Ultra Mirage full face. I have determined that I cannot abide anything up my nose because I have congestion many nights. So I bought the Mirage....am having leaks at the top and the bottom. If I shut the leaks off, I have marks on my face next day. I got the impression this thing is supposed to float on your face...well if it floats, I'm leaking! I've measured myself twice and I still keep coming up with a large which is what I have. I'm thinking about going to a medium. Cpap says all full face maks leak. see below...
Greetings,

You are going to get some leakage from a full face mask. You can try
and go to a smaller size, but there is no guarantee that it will work
for you either. You need to do the sizing guide and follow the
suggestions there. Here is the link to the sizing guide on our
website:

https://www.cpap.com/cpap-mask-sizing.php

Thank you for coming to us with your CPAP

I guess I'm looking for perfection, and maybe there ain't any in this world of hoseheads. Maybe a little leakage is okay...I just don't know. I do know this is frustrating as hell!