The Enclosed triplet is a very interesting form and if the a.b.a..b.c.b. format is used it forms the basis for the Sicilian Triplet , Terza Rima, using the enclosed word as continuity, or where lines or words are repeated there is the Villanelle, or later the Terzanelle.
The alternative left with is to have the centre unrelated completely as shown below
How would we know if our feelings are low
So low that teardrops stain porcelain faces
When faces are painted a warm loving glow
Which glows through when a lover embraces
If his embraces are few how may we know
Shall love flow when a tender heart races.
How can it be when true love hurts so much
So much it can break in two loving hearts
When hearts may respond to a sensual touch.
For touch prevents them from falling apart
Playing a part of true lovers games as such
To stop love from hurting is a work of art.
It could be that love came much too late
That it was never to be for you and me
For the love we had then was our fate.
Pasted from http://www.thepoetsgarret.com/2012Challenge/form1.html
My thanks to Divena Collins of thepoetsgarret.