APC is one company [out of a few] that is really on the ball when it comes to making props for specific applications.

I assume this 5 x 5.5 that IE is using is a competition series E prop..? There must be a whole class of speed plane out there that uses them. The class can be at "cult level" such as 1/2A CL Combat for example and they will still make a prop to fill that niche.

I don't think they make any props that do not have a well thought out and proven purpose ahead of time. They won't carry a size for very long that loses relevancy due to a rule change.

I can't say enough good things about APC because I fly a lot of "off beat" fairly specialized stuff and they have an outstanding prop choice for evey application.