Hey Camber, I'm glad you posted this question. I have gotten quite a bit of use out of my Peregrine this season, more than any of my other pack bags, and I can definitely say this is by far my favorite pack bag. Granted its not going to be enough for every application, but I find myself trying to use it any way I can no matter what or how I'm packing in.
I want to say you also utilized the EVO to REVO upgrade kit if I remember correctly? That's what I have. When using the standard bag attachments at regular frame height (no extensions), there is going to be a gap between the bag and the load shelf. However this whole past week when I was using the pack, I just put in my foam pad in that gap to use for glassing and it covered the space well. When I don't have something to put in that extra space, I'll often just take the load shelf buckles and actually connect them each to a higher buckle on the pack, criss crossing in an 'x' shape and it keeps the load shelf tight against the pack bag if that makes sense.
The other thing about this pack is that I've actually completely ditched the pack bag connections. I now solely utilize only the compression straps and have found that I love the way it then rides on my back supremely better. The awesome thing about the peregrine is the 2 different variations of how you can use the compression straps on each side. I find this super helpful to accommodate for different applications ex., hauling meat in between or just other dry bags etc. But when using just the bag by itself which I do a lot, I just use the compression attachments on the outermost part of the bag and not the true side of it. I can compress it down super tight and it just rides awesome. I love this pack.