Here's the 12" on the xtracycle:
http://flickr.com/gp/fletzet/XUtD13
And the 16" on the xtra:
http://flickr.com/gp/fletzet/2fNt56 or
http://flickr.com/gp/fletzet/CbZW0V
And one of the pictures that inspired me to get the bike:
http://www.flickr.com/photos/56062272@N00/2646331896/
We also attach the 20" on the xtra, but we don't have that well figured out with double seat. The 20's handle bars tend to rub into the back of the seat and are damaging it.