Maybe this is crazy... but... what if you were to make the same thing, but cut back a little on the fabric used? Maybe not back off to vinyl, but maybe just a cheaper (money-wise) canvas. Reading through the posts, the one thing I see over and over again is that many folks pretty much expect it to wear out, or to ruin it anyway, and do not want to spend much $$$. Lets face it, this is like 1/3-1/2 the value of the vehicle! I am a real believer in quality myself, and not consider my 4Runner "disposable" - however I'm not confident I will have it in 10 years... and much less 20. Even Jeep guys expect to replace their tops after awhile.
my point is, in this case it might be worth changing materials IF it will dramatically lower the cost - AKA go to a canvas-backed vinyl that is only $30/yard. I have bough that at my local store to make bikini tops w/ no problems yet.
Many people aparently just do not think the "quality is worth teh extra $$ - they;d buy by $$ first and longevity second. Just my 2 (more) cents.