Have you tried calling Charles on the number on the LOCT website?
I left a message a while ago when we were looking for a Non plastic seat and he called me back the same day, top man and VERY knowledgeable of riding hard and what is involved.
We ended up with 2 Co-Riders as our riding is far less off road biased.
We ride on Bridle ways and foot paths and on the road they are fantastic we called the helpline number on the co-rider website and talked to the designer of the Co-Rider. Very nice bloke and was very clear that bridle ways and smooth tracks are the limit of where the Co-rider should go.
He actually recommended the LOCT seat if our intention was to ride proper single track which was cool because he could have just claimed the Co-rider could do anything which he didn’t. I got a Co-Rider 2010 and my wife now has one of the 2011 versions which has a textured finish and better fasteners. She also got free shipping (which I didn’t!)
Think its horses for courses. If you intend to ride proper single track then LOCT if your happy to do the school and nursery run and bridle ways then the Co-Rider is great (and 1/2 the price). I don’t need the LOCT as I’m simply not a good enough rider to use it in the way it was designed.
By the way the 20Kg limit is quite alot, My daughter is 4 1/2 and still has plenty of room.