I would be kind of interesting to watch them truck 60 foot long plywood soffitts to the job site, woulddn't it. I'm sure that you could do this if it was rolled vinyl or aluminum. Straightening the aluminum would be kind of fun too. And how do you pre-locate the soffitt vents? You want the vents right in the middle of the rafter bays.
If somebody knows of a product like Leigh is looking for, please post the info.