the numbers if correct are too low. You should be looking for mid 50s. I would get another set of calipers and see if your numbers change. Also, try another piece of solder, SouthTexasBanshee has a great tutorial on measuring squish.
BUT your builder says run em, so im thinking the guy sells these set ups all day long and if he stands behind what he says run em, if theres a problem have him stand behind his work