EDIS for something different
 

I've been spending a lot of time lurking in these forums to learn all I can. First, what I'm up to.

I've spent the last decade building an airplane, a Dyke Delta to be exact. On the front, I hung a 13B, controlled with a MegaSquirt. Don't call me crazy quite yet. The way I've designed the system, I should be able get the engine started, switch over to manual fueling and then pull the MegaSquirt out of the airplane. There is a different set of problems and priorities that I have to work around, for instance, throttle response and warm-up parameters aren't nearly as critical as it is in a car, but there is a lot of overlap.

I'm running dual EDIS-4 ignition modules. Now, don't be hatin' on my EDIS choice. I needed a failure tolerant ignition system. I have them running off of separate power sources...one set running the leading and completely separate set running the trailing. I have the VR sensors situated so that there is an additional 15 degrees of advance. Add that to the 10 degrees from limp home mode, and I can have the ship's main power system go completely out, taking down both the MegaSquirt and primary ignition and still have significant power.

So, on to my question. I'm running EDIS but don't have the VR sensors set at TDC. It's off by 15 degrees. How do I compensate for this in Megatune? Do I enter a 15 degree trigger offset? Or is it better to shift all the entries in the spark table by 15?