Well, Tom has done it on cars he owns and has done it to others' cars. Would he do it if it was extremely unsafe? No, because things that aren't safe...like having a fuel pump sitting lower than your tank at the rear-most part of your car, is unsafe and he told one guy to fix it. Fitting it in the stock location would also be a hassle to run a filler neck to. It's possible, just more involved.
1992 Eagle Talon TSi - sold (POS)
2002 Mustang GT - sold
2002 SVTF - sold
2008.5 Mazdaspeed3 GT - cursed
2003 350Z Track - basically stock, and it runs