Sounds like they need to brush up on engine mounting techniques, and reinforce the firewall. I know it's to dramatically describe there was more thrust discovered by the change, I just wished these exaggerations would be avoided.
In my experience the plane was slower. I don't want it to move slower. 2 blade props have their application and so do 3 and 4 blade props. I avoid going over 2 blades, it's a personal choice, like avoiding some fuels, glow plugs, batteries, servos, etc. and I enjoy the speed my planes are flying at, and the more noise, the better. To each his own.