ah GeorgeS beat me to it!
After buying a smaller dell'orto collar I found that whilst the larger collar was too big for the bigger holed rubber elbow, the small one was too small, so as I had the PHBH26 I used the small hole rubber elbow which fits snugly onto the threaded carb outlet with a push.
It was however only about 7.5mm of 'lip' to attach to so I used a jubilee clip top to make sure it didn't shake loose and stopped 10 miles into the journey to check all as fine -which it was and my original casa performance filter came with a jubilee clip so I used that to ensure elbow & foam part were secure.
It stayed on despite Somerset's crap road surfaces (and Wiltshire worse ones) all the way home and still looks secure enough when the GP was put away.
It faces backwards as per GeorgeS's picture, the only different with mine is that it doesn't have the casa performance logo on it (and is therefore clearly a very rare prototype and is now up for a straight swap for any British registered GP200 electronic

)
Anyway -carb settings for this JIC it helps, the only things that were changed were the needle for my previous breath sweet which was running a tad rich throughout)
Mugello 225 on Mugello inlet manifold
PHBH26 BS
x7 needle 2nd clip (standard supplied needle on these carbs)
105 main
AV262 mixer
40 slide (standard supplied slide on the carbs)
50 choke jet & 45 idle jet
MBD clubman Mark II.