I usually do the same as the OP but use a full chimney. But from what I'm gathering my elevation at 7200 feet doesn't lend itself well to using smaller amounts of lit charcoal. With a full chimney and full ring of lump, it takes almost an hour with everything wide open to get to my target temps.
WSM 22 ~ WSM 18 ~ Maverick ET-732 ~ Flaming Fast Thermapen ~ Weber SS Performer ~ Weber 22 OTS ~ Weber 22 OTS ~ Weber 22 OTPlus ~ Weber 22 OTS ~ Weber Q300
When all else fails just ask yourself, WWGALD???