OK, it worked over night. Now I am actually seeing one confirmation for a tx which was done a few days after the split. I think I have to remove more block data still and remove it... Quite strange, so split must be well before file 949.... I may have to experiment a little with that then....
If your coins have not moved months prior to the split, you can afford to overshoot. Actually, you are better off overshooting and reintroducing files later, as the DB can append forward but needs rescanned backwards.