Hey mate,
Not sure how you will incorporate 2 straps into it. Here is a good tutorial, you could adapt it to what you have in your head...
http://www.youtube.com/watch?v=duflttCsTVw&feature=c4-overview&list=UULkCG-505-1t0rYlgBTSnpQ
I like his videos, they are great. I say, don't work to templates all the time and sometimes just start cutting and stitching!
Good luck.
Shags