Actually dutchy50, there are two cases here

1) Try and get a 14x6 or 14x7 (depending on what is available) and check ground clearence. If you feel you wont hit at landing or you fly off tarmac, you should use these props. They will offer lower top speed and greater accelration

2) If the 14xX prop is too large, try to get a 13x8 (The manual suggests that too as an option). Basically, as a thumb-rule, if you reduce dia by 1" you should increase pitch by 1. Be aware that the smaller prop will give you more speed so you will have to manage throttle at landing and fly in a more pattern than 3D sort of way (smooth accelration and deceleration)

Like everyone says, you will need to buy two or three props before you settle on what you are comfortable with. There is no harm in taking abigger prop. Keep it stock so you can use it on another model later. If you are concerned with durability or ruggedness get Master Air Screw. Their softer GRP material is more forgiving to ground strikes and mishandling and performs on par with APC atlease based on my experience.

I think 12x8 is too small for this engine, though others have been using it. I felt that 12x8 was more suitable for my 55AX. No bad feelings intended.

Personally, I tried 13x8, 14x6 and 14x4 on that engine. On my current FS- 91SII, I have put a 15x4 on the same airplane. The manual suggests upto 15x6 so ideal hovering prop would be 16x4 but the model is a UCD clone from Phoenix (called Topstar 3D) and that is the biggest size prop it can take. I have kept a 14x8 (as recommended by the manual) as spare in case the performance on the 15x6 is not good.

Ameyam