If you have 18 inch vented soffits on a hip roof, you are going to be very heavy on the intake Net Free Vent Area (NFVA). Meanwhile, when the roof is hipped, as opposed to gabled, you give up 2/3rds of the ridge line so that your capacity for ridge vent is greatly reduced.

International Building Codes suggest that you follow the 1/300 rule for static ventilation if you have a perfectly balanced ventilation system (50% intake, 50% exhaust, in terms of NFVA… or, you can drop as low as 60% intake to 40% exhaust… but you cannot go beyond this ratio of intake to exhaust and continue to operate with the 1/300 rule for ventilation.

So, you have 360 sf attic floor. Divide attic floor by 300 to get your total NFVA requirement. multiply that by 144 to convert to square inches. So you need 173 square inches total NFVA. (Hint: you are going to have way more than 173 inches NFVA in your soffit panels!). If you divide 173 by 2, you will have your NFVA exhaust requirement of 86 square inches. You can achieve this with 5 feet of a shingle over ridge vent, like the GAF Cobra III which specifies 18 inches NFVA per foot. But this means that you also need to limit your intake to 86 square inches, and just taking the attic floor of 360, I’m guessing that 3 sides of the roof will give you a perimeter of about 55 feet. If you are using perforated aluminum soffit panels, you are probably going to have over 1000 square inches intake NFVA. So rather than a 50:50 ratio intake to exhaust, or even a 60:40 ratio, you are going to have like an 90:10 ratio, or worse, intake to exhaust.

So your ventilation system is out of balance, and you cannot use the 1/300 rule to be within International building code compliance. You can use the 1/150 rule which effectively doubles the requirement for total NFVA, so we go from 173 to 346 square inches total NFVA, and your intake alone covers this requirement. IN this case, you should simply add as much ridge vent as you can to get your ratio of intake to exhaust as closely balanced as possible. But still, you will be far from balanced. But you will be in compliance with the 1/150 rule.

Now, all of the above is for “static ventilation.” You could think about using dynamic ventilation which does not use the 1/300 or 1/150 rule. CertainTeed has the best specifications for dynamic ventilation requirements. Take your attic floor, multiply by 0.7 (or 0.9 if the roof pitch is above 7/12), and this gives the CFM requirement. 360 * 0.7 = 252 cfm. A Lomanco 14" BIB wind turbine gives about 740 CFM in 8 mph wind speed (which is the annual average wind speed for Florida, and I would imagine is also similar elsewhere). So a single Lomanco 14" turbine would possibly be your best bet - as I’m not a big believer in unbalanced static ventilation systems.