you think it would be stiff enough for bigger robots?
a very subjective question, no?
You need to specify the exact forces you expect/estimate, do a force body diagram, then do a bending stress analysis. Otherwise you're just guessing.
(or you can buy/test it)
And then there are the issues that ArcMan brought up, meaning it depends on your tools and skill level, too.
(one day I'll write a FBD and stress analysis tutorial . . . one day . . .)