I am particularly fond of the weekender by Carl Friedrik and in the process of figuring out how to go about making it. Luckily, much of what I've learned here at LCMC can be incorporated into many aspects of this bag however the gusset construction is new to me. I've created several test pieces so I understand how the construction works but haven't made a bag using this technique.
The attached image shows the pattern I created as well as the actual CF weekender. I will be making the gusset slightly shorter and narrower to offset the thickness of the leather.
It also looks like the strip of leather around the gusset is made up of 4 strips - 2 "U-shaped" strips which match the curved corners of the bag and 2 straight strips which make up the sides of the bag. Not exactly sure how thick these strips need to be though. Just wondering if anyone has built something like this and has any helpful tips to share.

Probably the biggest tip would be that paper gets you close, but paper isn't 2.5mm thick, or whatever final thickness you'll use. Prototype using craft foam with a thickness as close to your leather choice as possible.
Also, the gusset could be one piece instead of four(?) on the CF. Not only will one piece make installation easier, but it'll look more premium too.