You can make the FLX tighter with a bit bigger fins.
The 132 is recommended with the 50mm, although there a number of riders who prefer the 40mm. If you have the 2004 FLX it is a little more skatey than the 2005/6. You can consider the 2.25-2.5cm heelside fins which will make the board a train...

BTW - here are some more photos on the brand new 2006 RRD XXXX boards:
