Beefed up Biffs

[LeicesterTiger]

I've started to do some research into the Bristol F2B Fighter, and although i've got a few books specifically relating to the Biff and the Squadrons that flew them, i'm yet to seriously get into them, for the moment have just looked at photos. One thing i've noticed is that 'Beefed up' Biffs (ie with twin Lewis' for the Observer, extra Lewis over the upper wing etc) seems to be exclusive to 22 Squadron.

Has anyone seen any photos or written evidence etc of other Squadrons doing so? If not, why not? In the 22 Squadron book 'Pi in the Sky' it mentions that although twin Lewis' was very desirable, at 8000 feet due to oxygen starvation, the Observer wasn't able to track aircraft fast enough with 'Huntley and Palmer' (a nickname for twin Lewis'), and at 16000 feet it became impossible for the Observer to move them at all.

I'd also be interested in anyones thoughts on the subject