The 55 is awesome. I was really lucky enough to have both a 55 and 65 with me at Eternity hole during my spring break. I was wondering if the 65 would work better. It was a great experiment because I got to switch several times and weigh the pros and cons.
The 65 was more comfortable, and yes, threw huge loops. BUT, it was very difficult to control. If i did get a cartwheel I would bounce and flush right out.
In my 55 I am constantly forgetting my overthruster and I still have great success. I get bigger loops than any boat made previously and it is absolutely the easiest to set things up.
Here is a pick from that day at eternity hole. I can't complain about the air time it gives up
If you are going river-running the 65 will be fun. But for serious play you'll love the 55 size
I hope this helps