Here's my take on the issue. I don't guarantee that everything is correct, but I haven't intentionally lied!!
I think you are right about using a traditional spraybar--it is up higher, so you would have more adjustment on an inverted engine setup, also, there would be less criticality if a profile installation where a uniflow vent is sometimes pretty far outside the spraybar. That being said, I have heard some people say that they see no effect of putting the spraybar more offset. I don't really understand why this would be so, but I haven't personally made such a test.
There is an article in an old issue of Stunt News where Scott Bair writes about our stunt engines. It is a really good article. One comment he makes is that he can get ~10-15% more power with a "true" spraybar-less venturi than with a spraybar type. I think what he is saying is that the air will flow with less turbulence and therefore with less pumping effort by the piston which has to pull in the air when it is moving up during the comperssion stroke. This costs some of the power from the engine.
Finally there is a question about the venturi pressure drop, which is what pulls the fuel in. Also in Stunt News, Frank xxx (sorry--I have forgotten his last name--but he use to write the SN engine column and he posts time to time at SSW) showed (as I recall), that you can get a better fuel pull with a spigot version on the "true" venturi. I can think of no reason not to want a good fuel pull, but I think it isn't supercritical with our 2 stoke Stunt engines, since we run relatively small venturi openings, so have a pretty good pull in most cases. We can compensate to some extent by opening up the needle. This may be different in 4-Stroke engines where you need to pull the air thru the intake manifold and the intake valve, so the air flow isn't completely limited by the venturi size.
Hope these ramblings make some sense.