Not sure on the prop really.. with an Apprentice... but I can say that if you're needing some ground clearance, you might look into bigger wheels. When you start switch props on an E-plane, you're getting into an area that you might need or want check your amperage before just taking it up. I would imagine that plane is pulling about 15-20 amps with a 11.1v Lipo.. which does put you at about 150 watts... maybe a bit more I'd bet.
See if you can find a moto-calc link somewhere, maybe even on this site that will give you some insight as to how to prop the plane... It's either that, or get yourself an amperage meter and check it yourself (not a bad idea at all really if you're going to be flying alot).. If you know the formula's and parameters you can safely make good decisions on your props, batteries, speed controls,etc...
What you're actually quoting at 150 watts says the motor/prop is only pulling 13.5 amps at 11.1v. That seems a tad low... I'm not saying it's wrong.. but I'm wondering how you arrived at 150 watts... to determine what/if you can go to a 3 blade without smoking your ESC or battery... The best way though is to probably drop a few bucks on a prop that you think will come close... It might be tough to find one... as the plane is specced with an 8.25x5.5 prop... If you can find a 7" 3blade prop... or even a 6" 3blade you'd be in the ball park to safely test your amperage... I'd bet a 6x5 3blade prop would be near what you need.... just a quick analysis here... but that's about what I'd start with and see where the amperage is.
The formula for figuring your watts is: Volts x Amps = Watts. ,,, but in my opinion the amps are the elephant in the room here.. I see the stock plane has a 1300 20c Lipo... so you're good up to about 25-26 amps there... the ESC though is only rated 18 amps... so if you prop it up too much.. that ESC will get very hot.. and that will create a problem.
I might even suggest keep your plane in top stock form and keep practicing with it... as you will eventually get into bigger faster planes.. These planes do fly very well. I hope this all makes sense here... and I'm sure there's more to it.. but this is it in a nutshell. Good luck with it.