That's a very interesting photo which I've never seen ( or anything quite like it ) before. All I can do is contribute a few random thoughts/guesses..... The theory about removal of weight sounds reasonable enough. From all the accounts I've read, it really seems that the front turret was little-used. The exception of course was the Dam Buster raid where the turret was manned throughout the raid, mainly to 'keep the heads down' of the German light flak. If the photo had been taken later in the War, I'd have suggested that this mod was undertaken for all-out speed, but in May '44 Bomber Command hadn't weren't heavily involved in daylight raiding. Also, if outright speed were needed, it's a little odd that the exhausts retain their fairings. I'd certainly agree that this is a non-standard modification ; as I'm sure you're aware records indicate that ND567 went straight from 32MU to 405 Squadron and wouldn't appear to have been selected for special duties elsewhere. I'm sorry not to be able to shed more light - but many thanks for sharing that image with us.