Good question jonno
so I had to attend he garage to remind me. I've got that 50amp chrome alternator remounted closer to the carbie. Add to that the 38/38 throttle lever gets too close to the dizzy top.
Even with the relative large adapter one of the throats needed to be machined in the adapter to angle the mixture southbound. Having thought about it more now I think its possible to do it all without an adapter but.....stuffing up the SPFI manifold wouldnt be good in the land of Oz eh.
Remember how the old vintage engine used to purr at idle due to their long/deep manifolds? maybe an advantage there with the adapter. Anyway, there was plenty of height above the engine of Tweety to mount a air filter cap and snorkel to fresh air ahead of one rear wheel. Both mixture screws are easy to get at and the idle. Those things would drive me nuts trying to adjust them if they were lower...even one inch lower. And you might be right, interference with the CV valve would be an issue. You can see the angle the adapter makes to level the carbie (and it still isnt real level!!)
The dapter cost $420. A mate of mine is an engineer and he spent all day on it. wasnt such an easy project he said and I believe him.
I recently adjusted the auto kickdown solonoid. it has transformed the trike. holds 2nd gear uphill till the flat road comes- perfect.
Getting a dyno this Friday in Shepparton. even more economy. hitting 30mpg without towing now. Exceeding my expectations.

[SIGPIC][/SIGPIC]Tweety trike- EA81 (full reco 2014) 32/36 weber, SPFI manifold, 9.5:1 CR, VW auto.