standing, paddling longer distances and the seat are the issues I see that most yaks cant do all at once. Standing means wide and stable which usually counters fast...the newer lawn chair type seats make sooo much difference in the all day comfort and helping to eliminate sore low back issues.... since you also want to do rivers extra long is not so good either...I would look at the Jackson yaks for the seat, standing and paddling ease...I have a T13 also, and it is a great yak, but it has the old seat pad design and it isn't nearly as comfortable as my new Hobie Outback with the new seat... I could never go back from the seat, but I could paddle again and do without the Hobie drive.