RevRobotics just released their FTC line. They have two different models. A 1 inch version (Mainly used in FRC) and a 15mm version (Designed for FTC). The 15mm extrusion bars have been available for the last year, with all of the new attachments being release at Kickoff this year. In the past teams were 3d printing their parts or cutting out similar parts.
I cant say that I have used this line of product yet, but my teams are looking into using the 15mm. We've created CAD models of the lifts that we would like to make, with some modification to the bars, but we're waiting on Andymark and RevRobotics to start selling the parts. We are looking at driving the slides with pulleys through a Cascading lift design with mini v-bearings we found on ebay.
As for weight and strength, I only have a 10inch piece of the 15mm that I got from one of their booths, and it weighs next to nothing. I can stand on it without it bending.
Attaching it to tetrix. I'm not sure how well it will line up with the tetrix hole pattern, as we custom build our robots, using as little tetrix as possible. But the brackets RevRobotics provide might work. If not, a drill and drill bit go a long way.
http://www.revrobotics.com/