Will it suffice? Possibly. It depends upon how you conducted your saturation curve.
1. If your saturation curve was done properly then you should be ok. This is because the trials for saturation curve are used ONLY for intensity determination, NOT time needed for proper part coverage. If your parts appear to be properly covered with a line speed of 3" per minute then you're in good shape.
2. If your saturation curve was not done properly then you might have some issues. The saturation curve requires incremental exposures to the shot stream, primarily by changing the exposure time which can be done by changing the feedrate. So, if your satruation curve is ploted against (inverse) feed rate you are probably ok. On the other hand, you could have left the line speed fixed at 2"/minute and then passed the Almen strips through the machine once, twice, three and then four times to give you the required four data points for the saturation curve. This method would also be ok since it is used to only reveal the peening intensity, not the time needed to cover your particular parts.
I hope this helps.
