Test results and safety factors

I am doing an analysis of an FRP structure that has the base flange anchored to a concrete footer. In order to determine the strength of the flange under load, a battery of tests were performed to failure. The results were fairly consistent.

My question is this:

To determine a safe working load, I used mean minus three (3) standard deviations (μ - 3σ) for a baseline strength and then used the ϕ of 0.65 on top of that.

But that has me wondering if I am being too conservative with the results. In my understanding, μ - 3σ is already a safety factor of sorts, providing a very strong reliability (~0.997). Combined with the load factors which are greater than unity, it would seem I have the safety factor built in, so to speak. On the other hand, if I used the straight mean and then applied the ϕ factor on top, this also would seem to be a valid approach.

Is one or the other acceptable or should I use both simultaneously?

For some additional information, here are the actual numbers:

Mean = 12.2 kN
Standard deviation: 1.43 kN
μ - 3σ = 7.87 kN
Mean with ϕ of 0.65 = 7.90 kN
Both reductions = 5.1 kN

It honestly looks like I'm doing overkill to use both simultaneously.