Guys...
To those who are interested in predicting actual thrust of a prop kindly browse this thread....

http://www.rcuniverse.com/forum/m_10933735/tm.htm

Well.... i should post it somewhere here, but under gasoline engine forum it feels more like home...

Hi!
A 1,50 four stroke can handle a 16x8 or 17x6 at sea level using 5-15% nitro fuel.
Never ever use a MA prop!!!! Those are the worst possible props to use!

Recommended props for sport flying suitable for most airplanes. All APC, RAM or Graupner Cam-prop!

Cox 0,049. 5x3 or 6x3
OS FP or LA .10 . 7x4 or 7x5.
OS FP or LA .15. 8x4 or 8x5.
OS FP or LA .25. 9x4, 9x5 or 10x4.
OS FP or LA .40. 10x6, 11x4, 11x5 or 11x6.
OS FP or LA .46. 10x7, 11x5,11x6 or 12x4.

ALL .40-.46 Ball bearing engines
like ASP, OS, Enya, TS, Kyosho GX, Super -Tigre, Magnum etc.
9x6, 9x7, 10x6 for Q-500 typ planes 130cm in span weighting 1,6-1,8kg
10x6 ,10x7, 11x6 for low winged sport aerobatic planes.
11x6 or 12x4, 12x5, 12x6 for all high winged or low winged trainers. The last one only for Kyosho GX .40-46 or OS .AX.46...possibly also TT.46 PRO SE

Four strokes!
OS.20 FS 9x6, 10x5.
OS.26 FS 10x5, 10x6, 11x4
OS .30 FS 10x6, 11x4
OS .40 FS 11x6, 12x4
OS .40 Surpass 11x6, 12x4
OS .48 Surpass 11x6, 11x7, 11,5x6, 12x4, 12x5.
OS .52 12x5, 12x6.
OS .90-.91 14x6, 15x4,15x6. 16x4W.
OS .1.20 16x6, 15x8
OS 1.60 16x6, 16x7, 17x6