Think that metal straping tape will be too heavy, I used fiberglass tape. Go with the stronger motor if you can I think the stock 280 and gear drive is underpowered. I built servo arm and motor covers as I fly on a frozen lake a lot and find that I have ripped off the motor mount three times on good landings and that the servo arms will hit the ground and break off soon. The plane glides and turns great but I have trouble keeping it up even with 45 deg of elevon throw!
Tried a APC 8x6 Slowfly prop, better but still a dog. Ground down and reamed out a GWS 8x4.7 orange prop and hope to try it in the AM if winds are less than 10MPH.
Really don't think you'll need a spar with the EPP wing and the lack of speed the plane has. Does look real cool flying in your face, just wish I could keep it up for more than a minute at a time. Am using 7 and 8 cell NIMH 750s.
Good luck and keep us posted as I have not seen any posts on this wing