Hi Marc,
that is a very good question......
which is one of many I ask myself, the top of the list being "why am I doing this?"
to answer the question you asked (and other may have wondered) is simply for long term strength.
This sculpt has to have an estimated lifespan of a few decades. Plus, it has to stand up to the actual move from Victoria to Adelaide, about4 or 6 car trips. (Adelaide and where I live in Victoria are about 15 - 18 hours drive apart)
Factor in the weather, Adelaide having very warm summers (avg 38 - 40 degrees Celsius) and these are some of the calculations that went into it.
I did not feel confident that the plastic wheels would live up to the regime of more then a decade, so I went for a lot of fuss and bother (and made things hard for myself) by over engineering it.
Better that, then 12 months later, every thing starting to droop or look wilted...
Probably is a lot of overdoing int, but have never done one before, so I thought that best build in some strength.
Good question though, I just mentally fast forwarded several years, and tried to anticipate the worst things that may happen, that I could control......
As for the kids kicking the football into while playing inside, well, even that is difficult to build against........
thanks for asking Marc!
Cheers