So if 21 is in use, how do you think you can get them lining up at 24??
Seriously, get rid of the ridiculous taxi slot time, halve(or better) the ATC workload by all the negotiating of taxi slot time, we early, we late, jamming Delivery with slot time requests because you have to get the time as soon as you get in the A/C, which, for us at least, is way out of our SOP for obtaining an airways(doubling up the calls...).
Does Perth need slot times?? NO