<VV> Two helicoils in line?

[chuck mckinley]

Tomorrow I'll be repairing a stripped head stud hole via the helicoil
method. I have one of the oversize Otto studs with a 7/16X14 thread at
the block end, but as it turns out, the old stud, which was standard
size, was already using a helicoil, and when it pulled out, it took the
helicoil with it and left a hole bigger than the drill size for the tap
for the oversize stud. Thus, I'll be putting in a helicoil appropriate
to the 7/16x14 thread size, and here's my question. The helicoil inserts
are only about half the length of the threaded part of the stud, and I'm
wondering if it's possible/smart/insane to drill and tap the hole far
enough to twist in two helicoils, one behind the other, to give the stud
that much more thread to grab. I've never tried this trick before,
although I've used dozens of helicoils of all sizes. One is tempted to
think that the threads tapped for the helicoil should automatically
force the helicoil inserts to line up in such a way that the stud
threads wouldn't get "confused" transitioning from the first insert into
the second insert (if you get the sense of what I'm trying to describe.)
For once, Google isn't providing any help with this question, so I'm
asking for your experience and expertise.

On the other hand, the oversize stud is so much bigger than a standard
Corvair stud at the block end, that maybe one helicoil insert is enough.
Assume that I'll use threadlock on the stud.

Suggestions, opinions, and comments are invited.

Chuck McKinley