Hi A-P..More trivia..If my memory serves me correctly (tempis fugit) we did operate both GT and HT rb211 versions on the -400, (the -H being used primarily to LHR/LAX etc out of Kai Tak)..As you alluded to, the ht variants had an increased maintenance cost vs the g's;;they basically had to come off the wing and go back to the shop more often..We haven't operated the rb -211's as an h variant for some time now...