Do you have any sort of meat thermometer? If so, cook them together and measure the heat in the smaller one... go to 140 or so for medium-rare. Then remove the small one and cover with foil and then a kitchen towel- let it rest until the big one is also at the same temperature.
OBTE wou will want a horseradish sauce... 1/2 mayo, 1/2 sour cream. horeradish to taste.
We are cooking one today as well.
Favorite Quote: "Time Flies Like an Arrow - Fruit Flies Like a Banana"