5.5 grams of DME in a 1000ml flask is about 1.002 SOG. Not enough sugar to build up a starter in 1 liter, let alone 1.7L. Many use 100 grams of DME per 1L to get roughly 1.040 SOG.
I've started using a lesser amount, 65 grams per 1L to get about 1.025 SOG. (I try to get my canned wort in the mid 20's as well.) Yeast will tend to work harder to produce alcohol in high wort concentrations and healthy biomass in lesser concentrations (Crabtree effect). Anyway when I look at the collected slurry, it appears to be at least as thick at 1.025 SOG as when I used 1.040. Just as much with less DME works for me.
This works best with well oxygenated wort, so aluminum foil loosely placed over your flask and a stir plate help considerably.