Reading Peter Wrights peice on carbon case design, he pointed out that both Stewart and Arrows attempted the design in 1998, with John Barnard at Arrows and Alan Jenkins at Stewart. Barnard had been working on Steel\titanium designs at Ferrari and had used a carbon bellhousing to accept suspension loads and act as an oil tank. Stewart dropped their design at the end of the year and Arrows carried on with it, with new designer Mike Coughlan taking over the project.
Prost did not get Barnards help until then and their restricted budget left Barnard focssuing on other areas of weight loss (uprights) with the use of titanium. So never got to follow the project up.