The JetCat P-130Rx we use is actually a 154N turbine as tested by RCJi and way lighter than all 112mm turbines. Yes, the ‘boom’ is the ducting, so the Evo is quieter, no problem with speed, I’m not full beans for 2 full circuits of the airfield yet ( needed for maximum speed) but it’s going to be in the 250+ class.
Grass makes little difference, we have two P-90Rxi (105N) UF in our grass club and both come out of a 120m strip with crop on 4 sides with ease.
Full ducting is better for protection, objects and fires. In the case of the UF the inlets are small so drag from removing the full duct is not so evident