I got underneath my V6S the other day with the intention of replacing the downpipes. However, I couldn't get my hand up near the top bolts, so I'm wondering if there's some sort of trick to this? Are people just using really long extensions to get to them?

 

I haven't attempted this particular task, but it sure looks like it calls for a long extension.
The flanged nuts really help on reassembly for that sort of thing too, because they don't drop into the socket while you're trying to get them started on the threads.