Yea, but if he wears a hat, you don't notice it

But he's right (as usual), while a bigger prop might reduce the rpm, you're pushing more air. So don't worry about the RPM, see how the plane preforms with that prop and use it or discard it accordingly.

PS, this is one of the reasons I tell people not to bother with a tachometer. I actually knew a guy who burned out a good engine by running it too lean - He was trying to get the 11,500 RPM out of a 12x6 that he was getting with an 11x7.