Add training load to .FIT file

I have a FR745 and a edge 800. On the FR745 I can se 7 day training load. The problem is that cycling activities recorded on the edge 800 does not count on the 7 day trining load. What want to do is to add training load data to the edge 800 .fit file so it will sync on the FR745 using Physio true up. Anyone with tips or solution to this problem?