I was planning to have it ready for one design at Nats but did not make it. The rules for that stated: “2017: Zingo (AMA or FAI) / Witchhawk 500 (AMA),with any class ‘A’ NFFS Nostalgia legal engine may be used for the Witchhawk and Zingo One-Design models. Will be able to fly in Classic Gas. The Zingo is also an Early FAI model and may be flown that way with the correct motor and weight.
So next year I assume I can fly it in A/B Classic, I will check out the rules for that.
Your Veco would fit Combined One Design. Either of your .19 engines can be used for AB Classic and A Gas.
For Vintage FAI (1979-V7) you would need a pre-1980 .15 engine and weigh at least 26.4 oz, or more depending on the combined projected area of the wing and stab. You would get a 7 sec engine run on 80/20 fuel (no nitromethane).
I know this is your first large gas model so a K&B GH .19 is probably not a bad choice, although as Steve pointed out that design was for the K&B 3.5. On my Witchawk 500 that I flew at the Nats the requirement for a nostalgia engine meant I used an OS 19, which is quite a bit lighter than the K&B 3.5. With a backplate mount, I had to move the pylon quite far back, probably an inch and a half from the firewall. This made the model somewhat squirrely in the climb and made having the right warps super critical. Ideally, the pylon should be right up against the firewall, so I would use an aluminum mount with your Greenhead .19 to get some weight up front, so that when you move the pylon forward or back to get the balance point it ends up as close to the firewall as possible.