Taxi per hourly basis

Kindly advise me;
Can we use a taxi by mileage +hourly basis in Da Nang?
If we are traveling about 50 KM but stay 4-5 hours and leave the place, what kind of transportation is ideal for?

You should deal with the staff of taxi company to set the amount you have to pay for the trip. Then, you don't care the meter and time it take.

Where will you want to go? Lang Co beach?

Thanks. We want to go to Hai Van Pass and next to Suoi Voi that is 15 KM north from Lang Co beach

It will be good trip. If you need help on dealing with taxi, please contact me at ipadhanh@gmail.com or blog da nang expats (website in my profile). All will be free, no fee.
Good luck!