The best I've got is to put carriers/LHDs on opposite sides of altis "off the map".. ie in the black area of the map. In this case, the "ships" can be over 60km away without problems... which is still rather small, but at least it takes a few minutes to get places. At 1200 km/h, that is 1 km every 3 seconds, so being 30km away from the center of altis means that it takes 1.5 minutes to reach the center, and 3 minutes to reach the other Carrier/LHD.
This I believe is a similar thread that may be of interest:
Particularly have a look at page 2.
Good luck. S