Jorge that is the style I have on my contender and it works great.
I would not go with less than 3 steps.
I can store mine on the euro transom but you can also lock them in place upright.
The Armstrong one I had the plastic steps broke off and it was useless.
If you don't have a platform in the rear (I have a euro transom) I would suggest a platform style so you have something to stand on.
http://1.bp.blogspot.com/-4aygEFiC59...Ladder+640.jpg