I had high hopes for using the equimeasure to accurately document my horses back shape, but was disapointed.
It was easy enough to follow the instructions and heat and mold the thermoplastic sheet to my horses back, but once I got home and relooked at the formed plastic, I thought, "Huh, that looks narrow". So I took my husbands orthopeadic calipers (Used for clamping across a persons hips - he is an orthopeadic engineer ) and used them to measure the width of my horse across the widest point of the ribcage and at the lower edge of the equimeasure sheet.
Sure enough the equimeasure sheet had closed up after removing it from my horse (I did wait until it was cooled to remove it). My horses width is 17" measuring with the calipers, and the equimeasure sheet measures 14".
Unless you have someway of measuring the width of your horse, I wouldn't be confident in using the equimeasure sheet by itself.
My 2 cents worth.