Well, I don’t know where my post went to so I’ll do it again.
If you want the ridge vent option, then I can suggest the DCI Smart Vent. It’s usually installed for houses without any soffit vents & it’s design requires you to cut a slot all along the deck from header wall to header wall, with shingles removed & then reinstalled.
Here’s a profile view:
For your application, install one on each side of the ridge line about 2 courses BELOW the ridge.
This means remove the ridge cap, then two courses down, set your saw @ 7/16" (assuming you have a 1/2" type deck) & cut your slot from L to R. Install the product, trim the new shingles where appropriate to allow the slot & then shingle back up. Repeat on the other side & then finally the ridge cap.
If you were to return the solar vents, I’d imagine the smart vent products & new shingles would cost less (the GAF solar units, with tax, will usually run you around 175.00 - 185.00 or so). One thing to consider is the difference in color on the new shingles vs. the existing ones. If your roof is ~6 or 7 years old, you’ve got a high probability of fading & / or algae staining on the old shingles & the new ones will probably look too different.
Either way, you DO need to plug all the old holes if you’re using a ridge vent type product & plus only the unused vents if you stick with the solar products.
Slight aside - I install a LOT of the solar units, so don’t think I’m a hater on that product. That you’ve considered 3 of them seems like a good idea to me.
Split the back slope of the roof into 3rd’s & place two accordingly, then the ridge over the front door area in 1/2 & place a vent in the halfway mark.
If you don’t want a solar unit in the “street” or more curb appealing side, you can put the back slope into 1/4’s & on these marks put 3 of them in place.
As for the humidity mentioned above, we do get a fair amount in Central Texas. When folks up North think of Texas usually tumbleweeds & the dry, high desert plains come to mind but believe me, that’s not the case around here. It’s no Florida, but we do get a lot of humidity during the late Spring, summer & early Fall.