I used a similar technique to make a boot puppet. I used some wal-mart sacks and tape and covered one of my husband's cowboy boots then cut the bag/tape cover apart at the "seams" and then I laid it out on paper and traced the pattern. It worked perfectly!
Here's the first boot I made - the prototype I guess you could call it.



I post this just to show the technique works!! I should have taken a picture of the process but I never remember to stop and take pics!