Nice explanation BlueSkye, but somehow it seems to be falling on deaf ears.
Tower Ranger, you can try and block slots for your precious aircraft ahead of time and you can accuse UH of doing the same but I can assure you that it cant happen. You wont be given a slot until about 15mins before the slot allocation period starts. It only affects TARDI/LABRI.
As has been said, go through the proper channels and things might be improved.