Radiant Barrier OSB Over Skip Sheathing--PLEASE HELP

Thank you so much for your feedback! So, our house is old (built in 1910) and only has the original wooden gable vent with a solar powered fan right behind it. From everything I’ve read, the original cedar roof was self-ventilating and no venting (besides that fan) has been added since. Now that we’ve finished sheathing over the skip sheathing we need to figure out the best ventilation possible for our scenario. Our scenario: hot and pretty dry climate in summer (not dealing with much humidity here in Escondido–inland in San Diego county also not a lot of rain), small home (very steep pitched roof with lots of open attic space which covers 864 sq ft of the house’s interior). My dad (also my contractor) did some blocking in the attic to make the house more structurally sound, so he says a ridge vent isn’t an option at this point (I think he also thinks they’re a pain in the ass). Also, because our house is a registered historical home and we are going to be applying for the Mills Act this month, I don’t think we should be doing a bunch of holes (soffit vents) on the top piece of wood siding of the house right under the eaves because it would be changing the look of the home. What would the next best scenario be? Do you think putting 2 low profile Ohangen vents on the top and bottom of each side of the roof is sufficient (for a total of 8 altogether, if that makes sense)? I think the code here is 1 sq ft of venting for each 150 as ft? I want to ventilated the best we can because A. It gets HOT here in summer and B. we are doing a dark charcoal GAF Timberline reflector series roof which is considered a cool roof, but I’m still worried about how hot it will get since it’s much darker than the lighter gray roof we had on our house (granted that was laid over another layer of asphalt shingles and over the original cedar shingles. My husband is way less concerned about all this and is deferring to my dad, but I am deferring to you! Thanks in advance!