Even though it seems your feeding too much, it goes to say that your other gaboon isn't vomiting. While the schedule isn't ideal, it likely isn't the reason for vomiting.

Carmichael's suggestions are perfect... the second regurg. often happens because the snake hasn't yet recovered from the first. Hydration is super important, and after a regurg. I"ll skip a scheduled meal and feed a smaller prey item (say, half the size of normal) when the time comes.

As always, re-evaluate your husbandry.

Ian