A more than 5 Amp but less than 10 Amp slow blow fuse on every single MOSFET's ground would be ideal. It would be cheep to do too, use slot style automotive fuses. (The colored plastic ones.) They are great for this kind of stuff. You can even solder to them. You want Red colored ones, as that's the code for 10 Amps. Red will be less safe than orange but less likely to blow prematurely on you. 10 Amps is still within the safe zone for our FET's.
If you try and gang everything together, to make a 55~75 Amp single point fuse, and you're running a low load, then just one single FET goes short, the total current will have to exceed 55~75 Amps before it blows that one main fuse. Not hard to imagine what is going to happen if you are running a low load and a FET shorts and dissipates 30~45 Amps through it for more than a few milliseconds.
Edit: When they are fully on, FET's can dump this many Amps no problem, but that's because they are not dissipating Watts when fully on. We can't expect a circuit failure to play nice though.
If you wanted to get a finer grain amp rating for your fusing or a bit more headroom, you can get 15 Amp fuses instead and gang up one for every two FET's. This gives you ~7.5 Amps effective protection for each FET when running a modest current. So if one goes short,his buddy is already dumping some amps to the fuse, then the head room is smaller for the short one. With this way you will only have to buy half as many fuses also. The only bad thing is that if your running low load and one decides to go more short circuit, that will be ~15 Amps X 24 Volts or 360 Watts. The transistors will only survive this for a very short time. Our cooling can only help so much before the thermal impedance of the package reaches it's limit. Though I suspect even this will be safe enough since we are not necessarily dumping all the watts in our transistor.
No matter what, 10 Amps or less per FET at 24 volts supply will not damage them as that's within there safe operating area.