Just purchased a Southbend OFE Stage 3 clutch from the US,

 

but is it worth installing a lightened flywheel (RPS or something similar)

 

some people say it is worth it, some say the difference is hardly noticeable.....

In my experience significantly lightened flywheels result in free-er revving of the engine in neutral (as you would expect, anything that lightens the load on the crank is a good thing), but once in gear there was a slight difference at best. At the risk of reducing structural integrity I'd leave well alone.

I was impressed when I fitted mine - a lightweight crank pulley as well makes quite a difference IMO :)

i have noticed a significant improvement with my Fidenza Ali flywheel which weighs 4.9kgs :)