The Topo-Duo is often mistakenly seen solely as a boat to teach beginners in. However, its real potential lies in the use by two experienced paddlers working together as a team. We regularly paddle steep creeks and big volume white water in my Topo-Duo. It's a completely different challenge to paddle the boat tandem on class IV and over stuff. This requires good skill as well as good communication and cooperation, so start out on easier stuff first untill you become a solid team!
Some remarks wrt its vices and advantages: Be _very_ careful when going over waterfalls, as it's very likely to pencil in if you don't have enough speed or the angle is wrong. The boat has little rocker and it will tend to go straight towards the bottom if you dive in vertically. The cockpit size is standard Eskimo size (very big!), that, in combination with the lack of central pillars, allows very easy acces and exit, which IMHO adds to its safety. The speed of the Topo-Duo in combination with the well placed mass of two paddlers allows this boat to punch or bridge holes that most other kayaks would sty in. This speed is also its disadvantage, making it somewhat harder to control through boulder gardens and on low volume creeks.
Buoyancy: Since this boat can contain well over 500 litres (~1100 lbs) of water, I have added a small airbag in front of the front footbace, a medium sized one in between the front seat and the reas footbrace, and another medium sized one behind the rear seat. That definately helps with the recovery, and it allows the partially swamped boat to be paddled to shore once one paddler has had to bail out!
Enders: This boat can easily be endered, you simply paddle forwards into a big hole (schnorkel mandatory for front paddler :-)), however, once you get stuck sideways in that same hole, it can be a real challenge to get the Topo-Duo out... Be careful there.
I love the boat, more for paddling with other experienced paddler than with newbies. They are made of very good quality blow molded plastic, which can stand a lot of (ab)use. New price in the U.S. should not be too bad, due to the good Dollar-Euro rate. Second hand they go for roughly $800, so you can use one for a couple of years and then sell it for almost the same amount of money. There is a lot of demand for them, so act quick when you spot one for sale! (did I mention that I love mine? :-))The BIG cigar has it's place on the river for sure. Great boat to teach newcomers boat lean crossing current differentials and coach them on stroke technique with you in the stern. I took the incredibly heavy outfitting out of mine and made molds from the seats and favbricated kevlar and glass seats and replaced the clunky bulkhead foot braces with Yakimas; estimated weight savings, 12#. This boat is heavy, but a real hoot to paddle. It's difficult to rescue after a swim due to the large open cavity in the middle and the difficulty finding adequate floatation for the ends of the boat. Takes some getting used to having only about 2' of stern behind the stern paddler. I added a minicell wall in the middle which did make exit out of the med. sized cockpits a little difficult. also put a custom carved chunk of minicell laminate in the bow for some floatation in the boat.
One of it's hidden selling points is that stacking it on its side on the car roof racks, allows you to literally stuff it full of paddling and camping gear when used in conjunction with good cockpit covers. The boat new is not cheap and I believe that may contribute to the lack of numbers of them on the water. like $1400 for a new one. I sold mine used (8 yr. old) for $800 and had its share of battle scars. Was never able to ender it due to the bulbous and short bow, but then it could've been the wate I was on. perhaps putting the heavier paddler in the bow for these exercises would be beneficial.. Only reason I sold it was financial, ie kids graduated into their own boats and it was collecting too much dust.