Totally up to you of course, and I myself have learned something on the merits or lack of merits of decoction generally (always did previously), at least my Baltic porter has 59% Munich, so for me, plenty of that character in the malt alone. Especially given the other dark malts and roast grain. Just my thought. Good luck - that's a great beer.
My wife is Estonian and her uncle Heino Pallo used to run the Tartu Õlletehas (literally, "Tartu Brewery") in Tartu, Estonia, under the Soviets through the liberation of Estonia on the USSR's collapse. Founded in 1807 by a Prussian family under the name A. le Coq, their family surname (they were actually French huguenot expats who left France for Prussia). They made a great Baltic porter.