So why do you want to add ridge vents? for ventilation? if so, why
don't you use powered thermostatic controlled vent fans inside the
gable vents, that's just what I did, I can't believe the temperature
drop in my attic of 3000 sq ft, from 160+ to now, around 100,
will save on the shingles, keep the insulation from absorbing heat,
moisture control, and save on my compressors run time also put foil
backed ductwarp
over my insulation leaving some space between for moisture to escape.

But, if it's for another reason, please excuse my interuption, didn't
mean to but in.

mrkool