Has anyone tried extending inside a vacuum cylinder?

The thought occured to me that if the stretched flaccid is greater than erect length maybe extending inside a vacuum might allow the erect length to catch up with the stretched flaccid sooner.

No, but I wait about an hour then wear an extender after I pump.

Extending and pumping - you bring up a good question. There are some problems getting a vacuum over an extender and this is why it has probably never been done (that I know of). However, at the heart of the matter is stretching PRIOR (if not at the same time) to pumping. Lots of guys ask: “should I pump flaccid or erect?” and/or “should I jelq before or after pumping?” Another option might be wear the extender for an hour or 2 before pumping to increase the effect of pumping on already stretched tissue.

I’ve thought of an extender built into a vacuum tube idea. But extending or hanging before you get into the tube, will provide a cock thats stretched more longitudinally and it usually pumps out just a little bit further in length.