I found this in the Ed Slott IRA discussion forum concerning ira rmd in year of owners death.
Seems it doesn't matter which inherited IRA is used or in what percentage to satisfy the owner's RMD (see alan-oniras' response).
Thanks for that link. This is the key phrase
This is what I recall, but inherited IRA procedures are very confusing and neither the IRS nor the custodians are helpful. In the case of an Aunt this led to distributions being taken twice the year she passed away, costing the beneficiaries an additional tax burden.They don't require it to be distributed equally to each beneficiary. If one of you needs the funds and the others do not, then that beneficiary could take the entire RMD and the other two would not have to receive a taxable distribution until 2011.
I do recall from discussions here and elsewhere that once the beneficiary IRA accounts have been established each one must take RMDs each year, they can't be offset by withdrawals from other IRAs or accounts.