Yes, Doug, the three or four bolts used for attaching these blades to a SkyWheels hub is pretty marginal but the 5/16 bolts through the nose weight may help some.

When Dick DeGraw was building DeBird (the partially powered rotor machine), he asked me about bolt strength as he planned on using these blades. Based on bearing strength, something like 15 each 1/4 inch bolts are required for a comfortable margin. Dick did a pull test in a hydraulic press and sure enough, the holes through the blade began yielding (failure in bearing) near the value I had calculated.

Based on this information, he came up with root attachments for DeBird that provide a comfortable margin. Root attachments should have a very large safety margin. Bensen always used a margin of about 10x normal level flight value and I see no need to go under that value.

The Scorpion 133 (2 seat) at Sun 'N Fun had 5 only 5/16" diameter bolts in each of the 2 blade grips.

This is a total cross-sectional area of 0.385 sq. in.

4 only 1/4" diameter bolts will have a total cross-sectional area of 0.196 sq. in.

1 only 1/2" diameter bolts will have a total cross-sectional area of 0.196 sq. in.