I had one & used it to find a saddle for a few different horses with good results. While it works well, as far as getting the shape of the horses back, care must be used when fitting a saddle to it. It is still slightly flexible after it "sets" so it's possible to make it fit a saddle, rather than have a saddle fit the mold. You can't just set it on a saddle rack & plop a saddle on top to see how it fits.
My saddle fit lady likes them also. She tends to use a solid wood type saddle rack & places a (small) rolled up towel in the gullet area of the mold, this helps it keep the correct shape.
They are nice when you can't get horse & saddle together in one place.
When I am using the EquiMeasure to find a saddle that fits I turn the saddle upside down and place the mold on it upside down. Mommy peanut is right, there is a little bit of flex, but not much. This works!
I don't post much on COTH. One could say that I lurk.
I've had clients send things like that to me, and they always seem to get crushed or warped in transit. One arrived after spending a week shipping in the summer from AZ, and it was nothing but a blob by the time it reached VT. IME, an accurate template and a good conformation shot are the best bets.
I am concerned that the horse I want to use it on won't stand correctly for the amount of time needed for the material to harden. I'm thinking the "poor man's" and "impatient horse's" substitute would be use a flexible ruler to get trace the spine to the last rib (marking "3 fingers back on the spine as well as 2-3" increments as you go back to the last rib). Then do a wither tracing "3 fingers" back from the shoulder blade, do tracings of back every say 2-3 inches (coordinate to spine measure with tape). Then cut vertical slots in back tracings so spine measure can "fit" into the back tracings. Wither and back tracings would fit into spine tracing at 90 degree angle.
Should result in an accurate model of the horses back for cheap. And it would not melt either! I'm going to try this and see how it goes. I will report back later.
The biggest problem I see with something like this is that you are fitting the saddle to the horse while the horse is at a standstill. Not when the horse is moving. Some horses will really lift their backs when in motion, so that a saddle that fits at a standstill will pivot once the back lifts up. I have a horse like this - he appears to have a slightly scoopy back when he's standing still, but he lifts his back so much when he's in motion that the panels start to pivot around the canter point, causing saddle pads to go shooting out the back. I have solved this problem by having a saddle with fairly flat panels, so that it bridges a TINY bit at the standstill, but when he moves, it conforms to his back. that solved my problem of shooting saddle pads.
Not saying that this device isn't helpful, but just saying that it only takes into account a horse's back when motionless.
"Opportunity is missed by most people because it is dressed in overalls and looks like work." - Thomas Edison
So, the Zen Buddhist says to the hotdog vendor, "Make me one with everything."