The other common problem is that the trust agreement doesn't cover the IRA. Your clients need an aggregate community property agreement that allows ALL community property to be considered when funding.
There are lots of income taxes to pay when the B trust is funded with retirement benefits. The RMDs are taxable income but not 100% trust accounting income - the B trust could be paying taxes at 35% on most of the RMDs.
I wrote an article for CalCPA magazine (or it's predecessor) a number of years ago but I don't think it's still available in cyperspace. Mary Kay Foss