2 bolts through the prop on the test stand is no problem, I run 3W 150s on my test stand with 2 bolts through the prop..The bolt are metric grade 12.9, same as US grade 8...Gotta be TIGHT...They don't break from being in tension, they shear if loose....That's why I like a single 3/8 grade bolt in the middle, no shear, will not break from tension..If it gets loose the prop just spins but won't come off....
