To be honest , i am considering going back to a clx 18 from the slx 18 , i love the slx but the clx is only 9 £1 coins heavier , and in the 18 footer flex is not a big issue .
And as Og said , on some stuff you need the flex , i have a fair few houses on one run where i used to use a clx 27 , now i use an slx 18 with 2 bottom sections of a clx 27 , and its a proper pain to get the bottom 6 inches of glass due to the houses having downstairs square bays with flat roofs .