I think this may work. Here is something to keep in mind. The fuel clunk comming in contact with the extra line could cause a problem. On 40% planes the tanks that you buy dont have ANY holes in them. You must drill the holes as needed. The lids dont crack or split do they? I know that there are some people that could find a something wrong with breathing oxygen and they breath black death to all around them but you have to ignor it and move on. Keep in mind that the big tank makers make universal tanks to fit every plane and not custome tanks as the need would be far to broad and they would be buisy making one off tanks for specail needs. I say do it. I think you have a great idea and you should run with it. good luck and keep us all posted even the people who fly in left circle after left circle with their Cubs and Telemasters.