Hi Ryan, love the scheme! You need to add a ton of weight to the tail. I filled the elevator tube with lead, and put the batteries right in front of the tailwheel retract. I don't think you need to reinforce anything but the front end. I put 6oz bidi carbon fiber from the firewall(which has to be moved back significantly, to the leading edge of the wing. You definitely want the long nose version for the twin, can't comment on the triple... I saw the triple in person last year, I know Thomas is keen on it, no way I would put that motor in this plane. Its just too big and heavy. Make sure you get the electric start, it is a must have! Love to see some close up pics of your Mustang.
Pretty sure I put pics of everything earlier in this thread on the reinforcements. The mounting kit I got was for the long nose, and I got the short nose motor.... (still bitter because I made it very clear I wanted the motor "for the CARF mustang") the mounting kit was near worthless this way, just served as templates. With the long nose it would be much easier.