No the engine is not 4.8 hp! That 25 pounds thrust is static at zero airspeed. People tend to forget... take three props of the same pitch and diameter, different manufacture......measure them and it is common to see the pitch off by as much as 50%. There is a reason why I have over 100 props. Great differences that can only be found by flying them....yes very expensive. The efficiency statement is not could be true it IS true. Look at prop efficiency vs normalized speed. Found in any book on aerodynamics. Yes a low pitch prop P/D ratio less than .5 has great thrust at zero but goes to hell as the speed of the plane increases. Higher P/D ratios maintain a greater thrust at speed. Those very low P/D ratio props became popular with the 3D ers. Look at the ubiquitous 10x6... good prop P/D ratio of .6. So why do I use a Xoar 22/10 3 blade on my corsair (P/D ratio of .45) well it is a scale plane and it looks good and performs to my satisfaction. Oh yes I have flown the plane with a Xoar 22/12 2 blade (P/D=5.5) and yes the performance was much better but way too fast for scale and did not look good. Check out the Moki guys. Most popular prop is a SEP 32x18 for slower models and 32x20 for the warbirds. Scary performance with the 32x20 (P/D=6.25) -Tom