I did pretty much the same thing with a Labcorp test last week. I used two 3oz bottles and a hand warmer. I put the bottles in hot water until the temp was about 104. I was wearing a pair of spandex with boxers over the top. Put the warmer down the front and stuffed the bottles down around my sack.....about 45 min later I took the test. I was nervous as hell because this was my first sub attempt. Nobody observed me, but I was given a 2 minute time limit. I'd done many dry runs making sure that the temp would be good and that I could get everything done without making too much noise, but I hadn't practiced a time limit. :wtf: My heart was pounding so effin loud that I was convinced the whole building could hear it. They drew a line on the bottle and said I needed to have at or above that line....turned out to be about 4 oz total. The temp was pretty much right on the money, about 97-98 deg. As far as I know I passed. Don't see any reason why I wouldn't have at this point.