Estimating Lacto to Yeast Ratios for Berliner?

So I am getting ready to brew up a split batch of Berliner weiss tomorrow, one of the buckets will receive an activator pack of the wyeast Berliner blend, and the other will be brewed according to the Brewing with Wheat book, by pitching a 5:1 Lacto to sacc ratio. Right now I have a finished 1800ml starter of lacto, and I was wondering the best way to approximate the 5:1 recommendation, as starter size doesnt seem to be appropriate since the growth rates of the two organisms is so different. Thanks for the help!

I think -- and I could be entirely wrong -- that in brewing with wheat it is intended that you go by starter size with the growth rates in mind.