You have obviously never ridden inverted forks mate. You wouldn't see Rossi or Pastrana riding forks that way up would you? ....and which way up are the forks the guys who just left Marzocchi just built?
I ride shivers and a lefty and would never look back.
Aaron Gwin rides what he is told to ride by people who pay him a lot of money. Haha, without MX and World Super Bikes etc and their massive R&D budgets, the mountain bike world would not be where it is today.
The greatest forces in any fork are on the tubes just below the lower crown. Do you want them to be thick or thin? Also where do you want all your unsprung weight to be? Low down as in an inverted fork, or high up in what is considered normal for the mountain bike industry?
they're not bad, and you could probably find em for about $250 used, and they don't need much maintenance at all, but they're really heavy, and don't offer as much adjustability as marzocchi is known for, plus the black sanctions don't work that smooth, but they're pretty decent, go for the nickel plated ones, you could find a decent used one from around 2008-ish for about $400.... I have friends who have the higher end ones from about the same year and they love them!
I ride shivers and a lefty and would never look back.