Here's a "dosing" page that Lantus has put up in regards to Type 1s who are just starting Lantus, or switching from NPH. They don't have a recommendation for switching from Levemir. When switching it's kind of a "wing it" at first. 60% sounds like as good a place to start as any.
The chart you'll see recommends 0.2 units per kilogram of body weight per day to start with. I put my weight in the chart, 268 lbs, and the chart recommends 24 units per day...which is exactly what I'm taking now. 24 units at night nets me a 95 mg/dL fasting blood glucose in the morning. Any less and it drives my morning numbers over 100 mg/dL. Any more and it drives me to the food locker. It seems you're a little more insulin resistant...so you'll probably have to titrate up from 60% until you find your magic number.
As an FYI here; Some people who inject a large dosage of Lantus have tried splitting their dosage as with Levemir. Either twice daily...or in two different spots with the same injection. The theory behind this is better absorption and avoiding the possibility of lipodystrophy, found here under Insulin Injections.