I used pvc plumbing pipe that I cut and butt glued to the shape that I wanted then wrapped the contraption with carbon fiber and epoxy. I coated the inside with tank sealer. I braced the carb to the frame to prevent stress cracks. I am sure it can be done if you want it to happen.
Having an efficient running engine is a big part of economy. Make sure your stock carbs are rebuilt. perhaps you can increase the length of the intake runners.
I am not much for driving a motorbike slow. It is a good way to get run off the road.
Stock there were two carbs that were nominally listed as 40 mm. My 34mm slide carb has more performance. I can open the throat fully rather than having to wait for the vacuum to raise the slides on the stock carbs. Strange but true. Each cylinder doesnt draw at the same time so there only really needs to be one carb per two cylinders.