https://moodle.org/mod/forum/discuss.php?d=233304#p1013910
Might be of some help - but please note as i commented in that thread, I have not been able to update it with work going on currently, although once 2.6 is stable and released I did plan to redo the backport to try to get the 2.6 changes into 2.5. (That is to make them available for anyone who wants to apply them - as Helen points out these sort of developments do not generally go back into core of other versions )
Richard