Thats the one to build. My kids grew up with a basketball goal made from 6" drill stem that had an arch of 4'. 30 bags of quick crete in the base.Drill stem, backboard (with goal, cement.....game time.
I pulled a few engines from that goal post as well.
Back to the OP. My buddy just bought a goal post for his kids. Put in one that is variable height so the little kids could shoot hoops too.
The problem is that when it's extended to full height, it's so wobbly that it doesn't really act like a basketball backboard. The backboard bounces, not the ball. Sucks.
Don't know the age of your kids, but that's what I've found.