I'm surprised that no other forum member has done this. I bought the slx 25 thinking it would cover all my needs but I have a few now where an extra section would make a big difference.
As far as i can see it's just a matter of buying the next size up section. I won't have the red and yellow warning rings but I can live with that.
I emailed Gardiners yesterday but no response. This is unusual as they are usually on the ball.