Like stated earlier, getting stuff even and symetrical, is super tough. It helps alot if the design is a little "loose". I have yet to try the 380, but 180 has been the best so far. 3951 conforms ok, but the adhesive to too aggressive for my taste. I've also had the edges of my top seam ripple up over time, whereas the IJ180 stays flat. As far as a template, every one is a little different and then factor different sizes into it! I just do a general measurement and have at it!
Here's a couple from earlier this year