Fishbed,. .Thanks.. .The only way I know to do this on any aircraft I have flown would be to put the pressurisation in manual and close the outflow valve. But this in my experience is always an emergeny procedure only i.e in a decompression.. .I am not an engineer but I suppose the amount of bleed air from the engines could be adjusted in the hangar, but this would constitute a major a/c mod. Any engineers out there been asked to do this?