I have a 70 Surpass 1 on my Astro Hog. I use a 13x6 Master Airscrew K series (the ones with white tips, supposedly 'four stroke' props). It flew great with this prop until a few weeks ago. The elevator fluttered (we think) and the horizontal stabilizer departed. It rolled inverted and glided a long way before it crashed. The repairs will take a long time.