Rule of thumb, longer prop with lower pitch= less speed and more thrust, smaller prop more pitch=less thrust but more speed. On a .46 sitting on a trainer you will probably never notice any speed difference between an 11X6 to an 11X8. I think the prop range on that engine is 10X7 to 11X8?? The owners manual will give you the starting points and you have to test the props until you find the one that you like the best. When I was still flying .46 engines in fun fly planes I ended up with the 11X6 APC as my starting point. On trainers I like to use the Master Air Screw props, they take ground strikes a lot better then any other prop I have used.