Here is a link to an interesting variation of ladder testing.
Long-Range Load Development
If you are getting good results at 200m start stretching it out and see what it will do.
Try 500m next. If good results get out to 700m+.
I think the best thing to do is get out and shoot at the range you want,
If it is a 1000yd load you want , you can get a good load at 500yds and then fine tune it at 1000yds. The vertical is the big thing at that distance.
The above link may help in the fine tuning process.