Dont want to knock the idea, but...
The elbow you have made could do with either insulating or heating. the problem is that the long length(maybe 6 inches on the outside of the bend) of steel pipe can cause the fuel to condense on the inner walls, leading to a 'wet' fuelling problem. A double skin with coolant running between, or maybe some copper pipe wound round the thing might work(with coolant runnin thru)
If thats not a possibility, mebbe some insulation/lagging, to try and keep the manifold from getting cold.
Su is a good carb to go for tho, works at better angles than Nikki/webber.
What the heck, give it a go, it may work spot on without any trouble.
:D