[aerohead]

As others have said,welcome! I noted your plans and here's my suggestion which dovetails into what others have already said.Consider all your options for driving technique and how that can impact your mpg,then consider a little more home work.I have posted a number of installments on aero-mods with some quantified results from published studies.I haven't done boat-tails yet,however you said you wouldn't be doing that so everything else you mentioned has been covered.If you will study the numbers,you should be able to "build" the Corolla on paper.If you were to rely exclusively on streamlining to push the car from 30,to 45 mpg,you would have to reduce drag by 100-percent,no mean feat! If you'll spend a little additional time going into the project you may spend your time much more efficiently.Happy fabricating!