I'm very interested in the gap filling mecanism and i think a new thread on it is needed. I did recently some CFD test with Solidworks and -15% cd reduction when a large gap between trailer and van was filled.
I'm think in someking of selfrolling canvas with the needed degrees of freedom and some magnetic help or a litttle kammback, or hundred of not clear ideas.
http://ecomodder.com/forum/showthrea...tml#post303838
in the attached files you could see
the van shape with cd=0.36
the van with trailer with equivalent cd=0.277
the gap filled one with eq. cd=0.233.