Around three (3) years ago, I did two trident maples fusing on two (2) years old seedlings; and I ground growed them since.
Today, 04/07/2012, I re-located the first one:

Fused trident 1 -- View 1

Fused trident 1 -- View 2
So, basically this a five (5) years old seedlings which have been fused for three (3) years.
This fusing has only seedlings, nothing in the middle. This is slightly bigger of the two. It is currently around one (1) meter tall. I will cut it to about 30 cm when I judge the time is right.