Maybe there is confusion as what a straight riser sump (engine) is.
The straight riser sump is what you need for an "A" model RV.
This sump has the carb. located farther fwd, and the induction tubes take a straight line path (only one bend) between the sump and the intake port on the cyl's.
A curved riser sump has the carb. located at the aft bottom of the sump (causes interference with the nose gear), and uses induction tubes with two bends in them.