Tibor,

One of my other colleages may have a slightly different twist, but I wouldn't necessarily file a 706 in order to establish the existence of a credit shelter trust. I would fund each of the sub trust as soon as possible, in other words try to use the administrative trust as little as possible to pay for the admininstrative costs of both decedents or to make distributions to the heirs. Make every attempt to comply with the terms the trust document that created the sub trusts. After the sub trusts are established each trust should bear its own costs. When the two trusts are terminated then make the proper distributions from each.