building a drum spinner

They are 2400CR each if that's the capacity?
Because it's a drum spinner it can only compete in robochalenge area anyway so I hope ground clearance will be ok.
I know there are only two robochallenge events a year but when are they?

2400mAh. Those cells should be fine to run both the weapon and drive from at 24v for a 3 minute fight. If you attempt to use one of the packs to power the drive and both for the weapon then you will be discharging one pack more than the other. A potentially dangerous situation.

Would my sabertooth 2x25 be able to handle two drill motors at 24v without blowing up?

24v is a bit of an overkill for the sabertooth, you'll need somethink like a victor 883 or a sidewinder

On dimension engineering's website it says it can take 6-24v nominal 30v absolute maximum, but I have heard that when put to it's limits it may explode, what do people think?

I've never tried it personally on a sabertooth, but going by the specs 2 drills on 24v would be fine on a 2x25a ESC.

Fully charged 24v packs could be getting close to 30v though so might be tight in that sense.

Could I protect it with some kind of fuse?

.....Or a voltage regulator or a Zener diode? Has anyone used any of these devices/components before?

The sabertooth is a nice controller but I have blown two in the past (they were replaced as I hadn't exceeded the specs but was at the limit).

I was running 2 18v drills on 24v worth of nicad cells. The interesting thing being, if I remember right is that the manual states that only 18 nimh/nicad cells should be used, well below 24v. I ran it with 20 cells. Initially the controller was fine but after a minute it blew (nothing beyond moving the robot around).

Stick religiously below the limits and it should be fine

Could I use a voltage regulator so that I only have 12v out of the 24v going to the drive system from the batteries but still have 24v going to the speed 900 motor to power the drum?