Elm Threadgraft Redo

This is the first tree I began to train as a bonsai two years ago.  It was a volunteer Siberian Elm tree from my front yard.  The original post is here

My first thread graft on this tree failed.  The grafted branch had begun to swell on the exit side so I assumed it was receiving sap from the recipient tree, but when I cut it off about 10" beyond the entry side, it immediately began to wilt.  I now realize that the swelling was a result of the cambium beginning to thicken due to constriction of the trunk around the branch, but the branch hadn't yet fused with the trunk.  I started a new thread graft in mid summer this year and planted both trees in the ground for faster growth.  I plan on leaving them both in the ground through next year and probably digging them up in Spring of 2014.  Instead of cutting the donor plant off, I think I may slice it lengthwise, cut a groove into the trunk of the recipient tree, and bend the donor trunk flush with the trunk, binding it with tape to cause the two trunks to fuse.  This should guarantee the graft doesn't fail, and also thicken up the trunk of the bonsai.