There are numerous studies I've seen with dosing. GHRP-2 studies can be used for dosing on GHRP-6, although the 2 analog is more potent (slightly) than the 6.
Via IV or a subq bolus, maximal dosing seems to be 2mcg/kg. Many long terms studies I've seen though don't use maximal dosing, more like 1mcg/kg.
The thing that worries me though is that from what I've seen, the GH response to these peptides dies in a couple hours (another thing thats awesome about the Merck drugs, they produce elevated GH levels for 24 hours, so you only need once a day dosing). So you might need to inject multiple times per day.
I think the best, if you wanted to inject once per day, would be 2mcg/kg subq, after a workout. If you could do 2x per day, I'd say once in the morning prior to eating and once post workout.