After much research into cutting holes in aluminum sheets, I decided to cut my top and back panels using hole saws. I found a great deal on all the tools I needed to cut 15/16" (close to 24mm) and 1&3/16" (close to 30mm) holes at
plumbersurplus.com. Check out what it cost me:
DeWALT D180015 15/16" Heavy-Duty Hole Saw $4.53
DeWALT D180019 1-3/16" Heavy-Duty Hole Saw $4.73
DeWALT DW1800 1/4" Shank Mandrel (Fits Hole Saws 9/16" - 1-3/16") $4.81
Shipping $9.27
Total $23.34
I think that's much more reasonable than buying lower quality saws at Home Depot for about double the cost.
Can't wait to get these tools so I can get moving on my stick!