Paul, let me share my ignorance, if you don't mind.
The Munich I have access to, at my LHBS, is American I think, and I don't know who makes it, but I believe it's about 10L.
Anyway, I'm leary of too much Munich. But, you're doing a lager, which is all they do in Munich, right? My beef with Munich is in ales, as it gets too "doughy" or something. I much prefer Vienna. The Vienna I have access to is light, so I assume it's about 3.5L, but I love how it increases mouthfeel and bread tones, but in a more refined way. The jury is still out in my mind regarding Munich in lagers, but it will be a long time before I attempt another 50% or greater Munich anything.