Super Tigre Carb Tuning

I am having a bit of a problem getting my ST 51 to run smoothly. I
have had STs before so I know you have a delicate balance between the
low end and high end before you get it just right. I recall reading
somewhere that the position of the spray bar is very critical as well.
Has anyone also heard of this? And what position would be ideal? Most
engines like it pointed straight down but I seem to think the STs
prefer a little upward thrust of the spray so if you are looking from
the needle valve side it would be pointed around 4 o'clock. Any
thoughts or experience on this? Many thanks.

Ted