I'm not sure if these are the plans you used or not, but I think they'll work. I plan on making one; maybe this weekend.
Those are the plans, I have a time saving suggestion after making this that could help. If your painting
it for finish make all slots 7/8" wide instead of tracing the board thickness as shown, I had to go back and do this as it was too hard to get some of the pieces together as the humidity changed from day to day. Also pay particular attention to the dimentions for the seat support width. I screwed up and cut it 4"then had to add 3/4X3/4" keys to the end for the seat locators which worked fine but ..... Anyway it was a fun project.
I went over all the edges with a 1/4" roundover bit in the router to get rid of sharp corners