How big can i go?

I read this from another section I think your size will not be an issue its about the amount of time it takes. Hardware wise I think it would only be what you would expect, more cable and hose length, more railing, more cable track.

Their could be voltage drop issues with more length but I think they would have already considered that when they put out the maximum size possible which I think is 50m2(squared) for the base one and double that with modifications.