LOL BIll, I got a highlander myself and really enjoy the ride. Never did figure out how many 2x4's it could hold though until I saw your post...and yes I have a baby's seat as well!!
I have been running a lot to Home Depot to get stuff for my new addition so I know how you feel when you look at the cart, then look at the Highlander and wonder..
"How in the ever living world am I going to put all this in there."
The thing is though, when you go into the BORG, you're only going to pick up a few things. The next thing you know, the cart is rounded over and your card practically melts when you swipe it through the scanner!!
I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"