DC10RealMan - 200kg may not seem particularly significant on a single sector, but imagine the cost of that on every GLA - LHR for a year!
How effective is height capping? I have been height capped many times, when operating outbound from UK Airspace. Typically the restriction is something significantly below FL300 until the UK boundary, but on EVERY occasion (apart from maybe a brief delay at the low, UK flight-planned level), the climb to near optimum FL has been almost continuous. So a big thanks to all of you who expedite our climbs through these "academic" restrictions.