Similar to your 5 gallon and decanting, but can't you just brew 5 gallons of lower gravity lager?. Send that over to a carboy for lagering and use the yeast cake for your dopplebock? I'd hate to see you decant off 5 gallons of scrapped beer, when you could get drinkable product with a little aging.
Primary #1: Empty #2: Empty
Secondary #1: Berry Rhubarb Wine #2: Black Currant Wine #3: Ice Shanty Bock
Kegged: Hidden Lake Nut Brown, Border Crossing Vienna
Bottles: 2H IPA III, Carmel Apple Cider, Spruced Winter Warmer, Big 50 Barleywine, Framboise Lambic, Dark Belgian Strong, Russian Imperial Stout, Sparkling Elderflower Wine, Barolo Wine, On Deck: ??