Now you can spend all day on the phone with IRS, complaining about how an EIN application allows the name of only one co-trustee. And why, in the case of trusts and estates making a Section 645 election, the 1041 instructions require the trustees to pick just one:

“If there is more than one electing trust, the trusts must appoint one trustee as the filing trustee. Form 1041 is filed under the name and TIN of the filing trustee's trust.”