Hi Steve; I havn't finally decided on engines for my 2nd Twin Otter I am sure in any case there will be enough room for tanks in the nacelles even with the longer 220 there will be about 3.5x3.5x4.5 for fuel which is a lot of running with these engines. The first cowl was pulled from the mold and is on its way for approval before I order large quantities. The laser cut kit has been finalized and should have production kits in a couple weeks with luck everything will be in hand shortly John