I'm not sure about specific amounts to use of the chiles but I would start out low, using maybe 4-5 and taste each day to see when you're happy with the heat and flavor. If you overdo it you can't back out the chile flavor/heat so it's easier to start low and if necessary add more peppers. I'd go as much as 7-8 days and if it still doesn't have enough, scoop out what you have and add more. I'd be concerned about leaving chiles in the beer too long would create some vegetal flavors (you could probably go longer but chiles are not so expensive it's worth risking an off flavor leaving them too long, I think 14 days would be the maximum I would ever go).
I have experience using larger peppers but I'm not sure how potent those particular chiles are.