7200rpm with a 28x10 BME prop still sounds high, if the BME prop is similar to a Menz-S 28x10.
A buddy's BME-110 on in-cowl mufflers turns an MSC 27x10 @ 5600 rpm.
I've never seen any 100-ish (3W or DA) motor turn a Menz-S 28x10 more than 6500 rpm. The Menz-S blades are fairly wide, but thin. The MSC blades are way thick at the root - look like a club.