Hi Brizzo, I have a 3D ARC S, I normally ski 4-5@35off (34 mph)
I tried the D3 EVO this summer and I found that the 2 skis are very similar in their "arc" (how narrow/wide the turn is) which made it very easy to ski on the EVO compared to my ARC S.
I didn't change to the EVO because I didn't feel that it would help my skiing (the difference being to little). The EVO felt faster but also a bit more unstable.
I didn't move the fin - just tried it with factory settings, so it might be "better" than the ARC, once you fine tune bindings/fin.
I wouldnt worry about the transition - its very easy comming from the ARC