Does a belt on a belt-drive bicycle stretch under load and then elastically return?
The only current manufacturer I know (Gates Carbon Drive) claims the belt does not stretch over its useful lifetime, but my question is does it stretch under load and then return?
I have read some forum posts (can't find them now), that say they stretch under load, so are no good for power applications such as single-speed racing. This argument would not seem to hold up since Gates now have a single speed racing team and they've won some races.
Does anyone have any factual information or practical experience that can answer whether the belt stretches under load and elastically returns?
A related question is if there is some slight elasticity would that help prevent the damage that can be caused to internal hubs from changing gears under heavy load?