For full resolution and no moire, you should have detail with both ISOs. Where one of them gets clipped, you will get half-resolution. If the subject doesn't have fine detail, half-resolution will not be noticeable; but if it has, you will get moire.
In shadows, this is less of a problem; you still have detail in both ISOs, but one of them has too much noise. That detail is usually enough to reduce aliasing, and the algorithm takes care of that. In highlights, if it's clipped, there's zero detail, so you just can't bring back the missing lines.
So, you have to be careful what is covered by both ISOs (OK) and what is covered by only one (risk of moire).
Try zebras with the higher ISO in LiveView: if the main subject is not overexposed, should be OK. Background highlights can be overexposed; if they are not too sharp (e.g. clouds), you will not see the aliasing at all.
This should also help:
https://bitbucket.org/hudson/magic-lantern/commits/84d446e1e06487fdf9a6cd1e3969ac717c84651c