Hi, I have done the exact same thing, actually just waiting to get them all back from the trimmers. the only problem I saw is if you fit these rear trims to an ADM sprinter, the rear seat will be too wide. If you look at the stock ADM rear inserts they are flat all the way allong the side of the car and go past the seat, but the JDM trims flare out and turn at the end to meet the thinner JDM seat. You'll have to install the top section JDM rear seat, or cut the 'wings' off the ADM top section and have it retrimmed. If you cut it then it has legaly got to be re-engineered because you've altered the structure of the seat.
Hope this helps