You can tune the bridle as well as your bar so that when you let out your trimmer all the way and pull the bar against the chicken loop it increases the final ratios of the bridle to greatly increase camber for more downwind angle. When I first flew my 15m, my flying lines were all equal length with the trimmer at full power and my bar against my chicken loop. In this setup, the Diablo line did not even engage. I shortened my rear lines a tiny amount so that being fully sheeted at full power induced some oversheeting (backstall) which helped me control the kite at the edge of the wind window, and also helped the Diablo line engage. Now that my bar has this oversheeting tuned into it, my "full power" downwind setting is letting the trimmer all the way out, then pulling it back in about 1".
I think the trick for tuning it is to get the kite so that it flies very well at full power downwind, then gradually increase the amount the Diablo engages until you find the sweet spot.
As highly engineered as Elfs are, they definitely need an experienced hand when setting them up for the race course, and their speed system is not the easiest to adjust compared to Flysurfer or the new Ozone system. I still don't feel like I ever really got mine dialed in correctly, but once I'm done with my post-injury rehab intend to spend a lot of time messing around tuning it.