DSII/Scout Walkers

Does anyone out there have a problem with the walker rules in DSII? 
Specifically, if I am following several threads correctly, y'all only
build
walkers class 4 and 5 (and 1 ).

I read that in the rule book, but did not take it to mean I could not
construct class 2 or 3 walkers.

I use the micro machine AT-ST from star wars as a class 2 light scout
walker.

Have I made a terminal error in the way I view these rules??