: I don't use redwood, too soft and brittle.

Brittle I'll agree with, but it is harder than WR cedar:
From the Forest Products Laboratory the measured Side Hardness, Load Perpendicular to Grain:
WR cedar - 350
Atlantic cedar - 350
Northern White cedar - 320
Redwood - 420

In other words RW is 20% harder than WRC. This agrees with my experience with the stuff.

My problems seemed to do with the chemical composition of the wood not being entirely compatible with epoxy. Shawn's problem sounds like a tension strength perpendicular to grain problem. In this redwood tends to be stronger than the cedars, but not much.

Redwood is stronger than cedar by many measures, but it has a lower modulus of elasticity ( 1.10 vs 1.11 WRC) and a lower work to maximum load (5.2 vs 5.8 WRC) and this agrees with your feeling that it is more brittle, it doesn't like bending and doesn't absorb much energy before it breaks.