But then the selection arrow on the unit is drawn in the wrong position. It seems to me that floatHeight is not taken into account to calculate the arrow positioning. Which means, in units with large floatHeight and small (relatively) standHeight, such in this case, the arrow is drawn on top of the unit itself. Pretty ugly.
Maybe this means that heights are not added to each other?
From the descriptions of the Ruleset Reference, I would draw just that conclusion.
upd: And, I understand, it swears if you try to create a unit with a standHeight of 20 and a floatHeight of 10? He says that in total, these two indicators can not be more than 23, 26? Then - yes, it is strange.
upd2: Alien Drone in FMP with standHeight: 11 and a floatHeight: 12 looks normal and no problem with the arrow... maybe if you make standHeight: X and a floatHeight: X+1 - everything will be fine?