Gumby's friend Tara?
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A quick search of this board for "contortionist" turns up a lot of hits but from many years ago. There are several guys with similar interests, e.g.,
http://www.theeroticreview.com/discussion-boards/boston-9/to-make-you-happy-will-post-my-favorites-from-another-agency-which-is-no-longer-around-181253
http://www.theeroticreview.com/discussion-boards/boston-9/check-out-piper-from-fl-145662
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Some are still posting / active. If they don't reply here, send a PM?

Very few and far between.  Best I found were a few that could do splits during the session.  Kimberly Posh was a beauty who did splits for me.  She told me she had been an NFL cheerleader.  Sashia was visiting Boston with RSG many years ago and she was a professional contortionist with a small circus in Oregon.  

Great memories [and nude pictures of both].  I recall they both did splits on top of my dick, but I was not able to shoot load during the short time they did.  Kimberly did splits while I stood above her for BBBJ.  I had a fantastic view looking straight down watching her BBBJ and directly over her ass in splits.

Such great memories in this hobby.  NEVER come close to anything like this in the "real" world.

Google "contortionist" (or "female contortionist") and narrow the results to "images" (or "videos").

I see by your reviews that you have been to NYC, so here is one suggestion:  Ivy Rose
TER ID: 286906
I would describe her as beautiful, petite and lithe.
I only met Ivy once, sadly have not been able to reconnect, but it was a terrific evening. She is  a dancer and very flexible, although I'm not sure of exactly what you're looking for.
This girl has a terrific personality, is multi-orgasmic, and you should be thoroughly satisfied when you leave..