I have bent 1/4" plywood over a 24" curve, but it's tough. Best to wet it a little bit... errr... make that "a lot"...
BTW, the nailer didn't work. The nails pulled right thru the plywood. We ended up using roofing nails and a hammer...
I guess I'm fortunate to live near a large city. When the plywood place in Pontiac no longer carried the plywood I wanted, I just called down to a place in Detroit, and had them deliver what I wanted.
Of course, if the place in Detroit no longer sells it, then I'll have to go to Boulter Plywood, just like many of the guys here have done...
http://www.boulterplywood.com/
It might cost a little more than buying it locally, but you'll get exactly what you want.
Mike...
The quality is remembered long after the price is forgotten, so build your teardrop with the best materials...