well, with towns above 5K I think it's not fair give advantages to players that make 2 clicks to place airports, 2 x couple more to build planes and more 2 to give orders... imo... totally unfair comparing to players that make rail/road tracks. So, with the actual settings... I can't agree. With some other suggestions to complete it... possible to think on...
Example: K1 server is with "multiple_industry_per_town = true" but required several tests to get a plausible number of towns ingame... to balance it... Combining the previous setting, number_towns = 4 and custom_town_number = XX (XX is the number of towns ingame - must be measured with map size)...