Hi Ana... OK, first of all, ditch that ball chair to sit on for the measurement.

I don't know if you saw any of my blab about sitz bones, saddle pain, bike fit, my wretched seat post design, etc. in your search but I am still looking for my saddle.

Part of my issue, well I hope it corrects 90th percentile of issues, is my bike doesn't fit. Have you had a "good" fit? And by "good" I don't mean one of those idiotic places that tells you "oh, looky honey, you can clear the top tube, it's a girly bike--you are a girly-yes?, then it fits--hooray". *pauses to vomit seething bile* (this was IME pre-days of finding TE of course)

Is the saddle put on *level*? Like with an actual tool that shows such. My stupid one bolt tounge-n-groove seat post would tend to shift one groove either way after I rode (even with really ratching it down) and un-leveled many saddles. It wasn't just my hand strength as a women either...

There is a thread I have in bike maint. about it. A couple peeps said even their lbs mechanics had an ill word for that design. That is on my list of bike hates for future buying.

I drove a ways to the Specialized dealer to get their sitz bones tests. Next closest town over from Mayberry got the Bontrager seat. I sat on that too. I used Play-dough with plastic wrap on the top and bottom. I also used a Pillsbury ready made pie crust dough rolled out between plastic wrap and waxed paper.

The bare hard top of a toliet seat is a good tip (take off the funky fuzzy lid cover of course if you own one). I did have a small step stool. If you have steps and they are carpeted, you can put something hard over the carpet. A bigger cutting board... metal cookie sheet, etc.

The cement stoop step to my fronch porch worked well. The tip you got about sitting on it just for feel first is good. Then set up your measurement mold stuff.

Also, if there is a way to wedge your hands underneath what you seating on and sorta pull your weight down, then hold, it helps to make the impression. Sit there holding the place until it starts to almost hurt (sorta like the saddle pain). Then, measure.

Lastly, if you use my pressue pulling technique to deepen your sitz bone dents... remember the soft glute tissue will spread out more... HOWEVER, the highest point of the sitz bone tip meausrement should remain unchanged. It doesn't matter how much the tissue mushes out, or there is of it, the bone structure itself is constant.

Good Luck!