Unless you had them all feeding of of one large fuel bladder the first engine would be out of fuel before you got the last one started. I think I would try to designing it such that it had 6 functional engines and the rear pushers would be free spinning just for scale looks. I have an 18 oz plane 30 in span trainer style plane that flys very well (not as slow as a trainer w/a Cox 6x3) with an AP Wasp .061 so think about scaling acordingly and using one 3oz tank for every two .061's or there abouts.