Question for Game Grognards

To keep my mind off Calidar's Kickstarter, I'm working on an air combat system for skyships and fantasy monsters, using concepts introduced in CAL1 "In Stranger Skies." This concerns the effect of wind direction and strength on skyship flight speeds. Depending on conditions, a skyship movement can be halved, unaffected, increased by a half, or even doubled.

Ideally, one ought to check a skyship's speed once at the beginning of a battle round. This enables unlikely exploits, such as starting the round at max speed, immediately turning into headwinds, and continuing the rest of the move at no penalty. Simple, but lacking a modicum of realism.

The other obvious option is checking one's speed after making each turn. The question with this is: how do I compute this? Say a skyship starts the round with its speed doubled due to a favorable wind angle, allowing for a total 12 hexes of movement. Halfway through (after having spent 6 hexes) the ship's speed should now be halved due to turning into a more unfavorable wind angle. What's the best way to calculate this? I'm defining "best" as not overly complicated yet somewhat logical at least.

I'm thinking that the remaining move should be half the skyship's base move (6 hexes divided by 2) since it already spent half its MV, divided by two again due to headwinds, equals 1.5 hexes, rounded up to 2. This becomes a real pain when a skyship moves instead 1/4, 1/3, 2/3, or 3/4 of its base move, and this exercise gets done every time each skyship makes a turn. Hmmm.

Any suggestions?