Determining max bending plane for a shaft with multiple belt loads

I've a situation where a shaft is driven by a timing belt, which then drives a flat belt. The drive belt tension vector is about 40 degrees from the driven belt. The drive and driven belts are not close enough together to be considered co-planar. I'm interested in bending at a bearing shoulder.

There should be a plane where the moments from the belt loads create a maximum. I'd thought to simply make function of Mcos(a-b), where a was variable angle, and b was the orientation of the belt load moment relative to a datum, and combine that with a similar function for M2. The moment diagrams have to be generated separately.

Is this reasonable? Is there a good example somewhere? All examples I found were perpendicular loads that could be combined with Pythagorean theorem.

thx.

I'm sure that the load is simply a single vector at some angle relative to the shaft and bearing shoulder.