@stephenkilborn Thanks for reaching out!
While the Co-op Cycles DRT 4.1 Fat Bike is not yet available for pre-order, we can help guide you to the best size for you. The size XL frame will have a standover height of just over 31", which should give you all the room you need. Plus, with long arms, you'll appreciate having as much length in the frame as you can get.
As a fellow fat biker I am super excited for these bikes to come out! We'll circle back with the Co-op Cycles team and see if we can find out some more information about when they will be available. We'll respond here in the community when we hear back.
Hope this helps, thanks!