Hi Frank,
I like your poem and can't see that it's 'maybe not
The Oldie's cuppa'.
At first I thought
shell-shorn would be better as
shell-torn, but I've since changed my mind; I think you have it right.
Just a few suggestions: I would put a semicolon at the end of L3, and the age-old argument for/against initial capitals looms again! Personally, I think this poem would read far better without them; to begin with, I read that 'But' as being the start of a new sentence. A comma would help after 'Mars'.
The barren, shell-shorn place resembles Mars,
but for a galaxy of large round shot
'atop the road' seems a little odd to me. Wouldn't 'along the road' do?
In the last line, three dots are usual for an ellipsis, and why not end with the slightly more punchy . . . Balls. with a capital 'B'?
Hope this helps a little