Paul, this is the relevant point from the rules.........
"1.6.11 Fuel Tank
Fuel tanks must be either OEM Ducati OR made of steel or aluminium.
Fuel tanks with tank breather pipes must be fitted with non-return valves that discharge into a catch tank with a minimum volume of 250cc made of a suitable material."
The later 620ie's are supplied as standard with the "plastic" tanks, so the "OEM" statement validates these as OK to use.
Just watchout for the catch all phrases that we have put in them, wouldn't want anyone to fall foul and be excluded.
In the event of any doubt as to the interpretation of the Rules, entrants should mail desmodue@ducatisportingclub.com and we will give a written response. That way your bright ideas will stay private!
With respect I was only kidding! However, look at all the great motorsports. Fi, rally, WSB, GP, they are all after an angle, I think thats all part of the sport!