I believe the BME props might be a little more narrow. I have never run an MSC, but I have seen them and they are a lot of wood for sure.

As for your friend and his MSC 27x10, that doesn't sound right. I have lost all my notes for my engine, but I know it was swinging a menz clone (3w) 27x10 at about or above 7000 when brand spanking new. So to only be able to spin an 27x10 @ 5600, something is wrong, That's over 1500 rpm difference!!!
Beside that, the engine is going to needs to run in the mid 6's for performance AND that is straight from the horses mouth.
(and I know there can be a wide variations between same props from the same manufacturer)